The basic gist:
--consumers spend  on average 20% more when they aren't using cash.

--Mastercard/Visa charge small businesses 3% - 5% of the transaction cost.  This more than offsets the 2% GST tax cut that Stephen Harper did in 2006

--cash buyers help average down the cost of the credit card tax for small business owners

A small physio clinic owner I know pays $25,000/year in credit card processing fees.  That's the equivalent of one minimum wage worker's pay for a year.