What happens if a purchase is $0.02 in Canada?
As someone who works for a company that deploys POS systems in Canada, I can tell you that your best bet would be to have a configuration option that lets the client decide what to do. If they have a business practice that would allow for a sale total to be $0.01 or $0.02, they should first evaluate their business practice.  If you're building a POS system to deploy in Canada, I'm sure you have access to resources (potential clients) who would already know how they would want to handle this. Ask them. The rounding should always follow the same rule. If the value ends in .01 or .02 then you round to .00. Doesn't matter if it's 10.01 rounding to 10.00 or 0.01 to 0.00. The decision on what a company wants to do if an invoice total is $0.01 or $0.02 would be up to the company. The POS system should follow the rule and round to $0.00 if the method of payment is cash, but the company has the right to not give things away for free.  They can impose a minimum cash invoice amount of $0.05. But you would do this by requiring the customer to add more items to their purchase. You couldn't just round the invoice up to $0.05 and to charge them $0.05 for a $0.01 item It would be similar to companies having a minimum purchase amount when paying by credit card. If their minimum amount is $10.00 and you want to buy something that's $5.00, you either pay cash or add something to your order. They don't just charge you $10.00 for your $5.00 item. I think this would be a extreme edge case where you have an invoice with a total of $0.01 or $0.02, without any discounts, partial payments, etc. If the customer's total was $10.01 and they paid with a $10.00 gift card, the final amount owing of $0.01 would round down to $0.00 and they wouldn't owe any more. If they had paid cash, the total would have rounded to $10.00 anyway.  Similarly, if the customer returned an item and bought a new item, or used coupons, and the total owing was $0.01 or $0.02, then you would round down to $0.00 and they wouldn't pay anything. As BobbyScon said, you can implement some options to allow the company to decide how they want to handle this. You could have an option that doesn't allow a sale to be processed if the total amount is less than $0.03 and the sale doesn't include any discounts, returned items, coupons, etc. The option could be to completely block the sale, require a supervisor override, or just display a warning to the cashier. Best bet is to talk to as many of your current or potential clients as you can to see how they would like this edge case handled. For many, it's probably a mute case since they wouldn't have items that have a unit price less than $0.03. Maybe a place like a hardware store that sells individual nuts, bolts, and washers. I'd imagine in this extreme edge case it would round down to $0.   I can't fathom what makes $10.02 or $153.02 any different from $0.02. I think it should be free. Why? I had a coupon for 35, I bought something for 35.01 including taxes and total to pay was 0.01, rounded to 0.00. I think it's almost the same scenario.
"@sdg's answer is spot-on with the advice to avoid repeated conversions, but I'd like to provide some specifics on the fees involved: Each time you round-trip Canadian dollars (CAD) through a U.S.-dollar (USD) priced security at TD Waterhouse and leave your proceeds in CAD, you're paying a total foreign exchange fee – implied in their rate  spread – of about 3%, give or take. That's ~3% per buy & sell combination, or ~1.5% on each end. You can imagine if you trade back & forth frequently, you can quickly lose a lot of money.  Do it back and forth ten times in a year and you're out ~30% on the fees alone! The TD U.S. Money Market Fund (TDB166) that TD Waterhouse is referring to has no direct commission to buy or sell, but it does have a Management Expense Ratio (MER) of 0.20% per year – basically a fee which is deducted from the fund's returns (which, today, are also close to zero.)  Practically speaking, that's a very slim fee to hold some USD in your Canadian dollar TFSA. While 0.20% is cheap, a point to keep in mind is if you maintain a significant USD balance, you are maintaining currency risk:  You can lose money in CAD terms if the CAD appreciates vs. USD. Additional references: Canadian Capitalist describes TD Waterhouse and the use of TDB166 and ""wash trades"" at How to ""Wash"" Your Trade?  He's referring to RRSPs, but the same applies to TFSAs, which came out after the post was written. Canadian Couch Potato has two relevant articles: Are US-listed ETFs Really Cheaper? and Lowering Your Currency Exchange Fees." So in your screenshot, someone or some group of someones is willing to buy 3,000 shares at $3.45, and someone or some group of someones is willing to sell 2,000 shares at 3.88. Without getting in to the specific mechanics, you can place a market buy order for 10 (or whatever number) shares and it will probably transact at $3.88 per share because that's the lowest price for which someone will currently sell their shares. As a small fish, you can generally ignore the volume notations in the bid/ask quotes. In theory, when you obtained ownership of your USD cash as a Canadian resident [*resident for tax purposes, which is generally a quicker timeline than being resident for immigration purposes], it is considered to have been obtained by you for the CAD equivalent on that date.  For example if you immigrated on Dec 31, 2016 and carried $10k USD with you, when the rate was ~1.35, then Canada deems you to have arrived with $13.5k CAD. If you converted that CAD to USD when the rate was 1.39, you would have received 13.9k CAD, [a gain of $400 to show as income on your tax return].  Receiving the foreign inheritances is a little more complex; those items when received may or may not have been taxable on that day. However whether or not they were taxable, you would calculate a further gain as above, if the fx rate gave you more CAD when you ultimately converted it. If the rate went the other way and you lost CAD-value, you may or may not be able to claim a loss. If it was a small loss, I wouldn't bother trying to claim it due to hassle. If it's a large loss, I would be very sure to research thoroughly before claiming, because something like that probably has a high chance of being audited. "Occassionaly a trader will make a blatant mistake. A customer calls to buy 100 shares at $10, and the trader by mistake enters ""10 shares at $100"". You get one very happy seller :-) In the USA, it doesn't happen often for sales, because if the trader offers to sell 10 shares at $100, there will be nobody accepting the other.  In Japan, with one dollar equal to 120 Yen, the same mistake would mean that someone wanted to sell 100 shares at 1200 Yen, and the trader enters 1200 shares for 100 Yen, then you will get a happy buyer, and a massive loss." You should start a dispute with the credit card company, and they might be able to recover some/all of the money. Usually, if you act fast enough, credit companies (on the merchant's side) have enough of the deposits not yet disbursed to the merchant, and they'll just reverse the charge. The earlier you start the process - the more chances you have. Otherwise you'll have to sue, I'm not familiar with the Canadian legal system. If you aren't familiar with Norbert's Gambit, it's worth looking at. This is a mechanism using a Canadian brokerage account to simultaneously execute one stock trade in CAD and one in USD. The link I provided claims that it only starts potentially making sense somewhere in the 10,000+ range. Could you not just say that you had bought it when it was pennies on the dollar and made the millions that way? There isn't much of a transaction record, is there? I also just realized that I don't understand how taxes work in that situation. If you have a different currency from the U.S. Dollar, and it increases in value greatly, do you have to pay tax on that increased value relative to the U.S. dollar? They don't when it's minimal increases. Suppose you're a European Company, selling say a software product to a US company. As much as you might want the US company to pay you in Euros they might insist (or you'll lose the contract) that you agree pricing in USD.  The software is licensed on a yearly recurring amount, say 100K USD per year payable on the 1st January every year. In this example, you know that on the 1st Jan that 100K USD will arrive in your USD bank account.   You will want to convert that to Euros and to remove uncertainty from your business you might take out an FX Forward today to remove your currency risk.   If in the next 9 months the dollar strengthens against the Euro then notionally you'll have lost out by taking out the forward.   Similarly, you've notionally gained if the USD weakens against the EURO.    The forward gives you the certainty you need to plan your business. If you want to convert more than a few thousand dollars, one somewhat complex method is to have two investment accounts at a discount broker that operations both in Canada and the USA, then buy securities for USD on a US exchange, have your broker move them to the Canadian account, then sell them on a Canadian exchange for CAD.  This will, of course, incur trading fees, but they should be lower than most currency conversion fees if you convert more than a few thousand dollars, because trading fees typically have a very small percentage component. Using a currency ETF as the security to buy/sell can eliminate the market risk. In any case, it may take up to a week for the trades and transfer to settle. You shouldn't be charged interest, unless possibly because your purchases involve a currency conversion. I've made normal purchases that happened to involve changes in currency.  The prices were quoted in US$ to me.  On the tail end, though, the currency change was treated as a cash advance, which accrues interest immediately. "When you hold units of the DLR/DLR.U (TSX) ETF, you are indirectly holding U.S. dollars cash or cash equivalents. The ETF can be thought of as a container. The container gives you the convenience of holding USD in, say, CAD-denominated accounts that don't normally provide for USD cash balances. The ETF price ($12.33 and $12.12, in your example) simply reflects the CAD price of those USD, and the change is because the currencies moved with respect to each other. And so, necessarily, given how the ETF is made up, when the value of the U.S. dollar declines vs. the Canadian dollar, it follows that the value of your units of DLR declines as quoted in Canadian dollar terms. Currencies move all the time. Similarly, if you held the same amount of value in U.S. dollars, directly, instead of using the ETF, you would still experience a loss when quoted in Canadian dollar terms. In other words, whether or not your U.S. dollars are tied up either in DLR/DLR.U or else sitting in a U.S. dollar cash balance in your brokerage account, there's not much of a difference: You ""lose"" Canadian dollar equivalent when the value of USD declines with respect to CAD. Selling, more quickly, your DLR.U units in a USD-denominated account to yield U.S. dollars that you then directly hold does not insulate you from the same currency risk. What it does is reduce your exposure to other cost/risk factors inherent with ETFs: liquidity, spreads, and fees. However, I doubt that any of those played a significant part in the change of value from $12.33 to $12.12 that you described." From a purely financial standpoint, you should invest using whatever dollars get you the best rate. The general rule of thumb that I've come across is that if you are making another person/company change your money into another nation's currency, they will likely charge a higher exchange rate than you could get yourself. However, it really depends on your situation, how easy it is for you to exchange money, what your exchange rate is, and what your broker is charging you to exchange to USD (if on the off chance this is truly nothing, then stick with CAD). Don't worry about the strength of the USD to CAD too much because converting your money before you make purchases doesn't allow you to buy more shares. For the vast majority of people, trying to work with national currency exchange rates makes things unnecessarily complex. * They have to accept some responsibility for submitting the order multiple times.  * If the price had gone up, would UBS be offering to return the shares they didn't mean to purchase?  * It hasn't cost them anything yet.  Not unless they sell the shares before the prices goes back up (which it likely will eventually). I want to shop in the currency that will be cheapest in CAD at any   given time. How do you plan to do this? If you are using a debit or credit card on a CAD account, then you will pay that bank's exchange rate to pay for goods and services that are billed in foreign currency. If you plan on buying goods and services from merchants that offer to bill you in CAD for items that are priced in foreign currency (E.g. buying from Amazon.co.uk GBP priced goods, but having Amazon bill your card with equivalent CAD) then you will be paying that merchant's exchange rate. It is very unlikely that either of these scenarios would result in you paying mid-market rates (what you see on xe.com), which is the average between the current ask and bid prices for any currency pair. Instead, the business handling your transaction will set their own exchange rate, which will usually be less favorable than the mid-market rate and may have additional fees/commission bolted on as a separate charge.  For example, if I buy 100 USD worth of goods from a US vendor, but use a CAD credit card to pay, the mid-market rate on xe.com right now indicates an equivalent value of 126.97 CAD. However the credit card company is more likely to charge closer to 130.00 CAD and add a foreign transaction fee of maybe $2-3, or a percentage of the transaction value. Alternatively, if using something like Amazon, they may offer to bill the CAD credit card in CAD for those 100 USD goods. No separate foreign transaction fee in this case, but they are still likely to exchange at the less favorable 130.00 rate instead of the mid-market rates. The only way you can choose to pay in the cheapest equivalent currency is if you already have holdings of all the different currencies. Then just pay using whichever currency gets you the most bang for your buck. Unless you are receiving payments/wages in multiple currencies though, you're still going to have to refill these accounts periodically, thus incurring some foreign transaction fees and being subject to the banker's exchange rates. Where can I lookup accurate current exchange rates for consumers? It depends on who will be handling your transaction. Amazon will tell you at the checkout what exchange rate they will apply if you are having them convert a bill into your local currency for you. For credit/debit card transactions processed in a different currency than the attached account, you need to look at your specific agreement or contact the bank to see which rate they use for daily transactions (and where you can obtain these rates), whether they convert on the day of the transaction vs. the day it posts to your account, and how much they add on ($ and/or %) in fees and commission. "I don't know Canada very well, but can offer some general points when considering where to park your emergency fund. Savings rates are currently low, but then so is inflation. Always bear in mind that inflation decreases the value of your money, so if you're getting 4% interest and inflation is 2%, you're making 2% gross in real terms. If you're getting 2% and inflation is close to zero, you're actually earning a similar amount, it's just the numbers are going up more slowly. Obviously when and how much tax you pay affects the actual return, it's just worth bearing in mind that low interest and low inflation are actually not that bad a savings environment as they first appear. For an emergency fund the key thing is ease of access, consider keeping some portion of your savings in an instant access account for those emergencies that happen when the banks are closed. In the UK there are various tax-free savings options, I'm guessing Canada has a few too, if so you should explore those options. While these may not have attractive headline rates, you don't pay tax on the interest, this can make them much more competitive (4% tax free is the same as 5% gross if you would have to pay tax at 20%). Normally tax free investments have caps so once you've invested a set amount you can't add anymore. This may be a consideration if you regularly dip into your emergency fund as you might not easily be able to build it up again. My approach is to have about 90% of my ""rainy day"" fund in easily accessible but tax free savings. This discourages me from spending it unless I really need to. I then keep a slush fund sufficient to cover every day disasters (boiler packing up, needing a hire car for a week etc) in instant access accounts ."