What if the value cannot be accurate to one decimal place? I have read a lot of papers, and the tables they draw are accurate to one decimal place. But my data looks like this: 0.003% 12.736% 19.255 and so on. If it is accurate to one decimal place, 0.003% is zero. There are three more data in my table: 5.265*10^8  6.840∗10^4  2.213∗10^3 and their sum is 5.266∗10^8, but if I am accurate to one decimal place, it becomes 5.26∗10^8 6.84∗10^4 2.21∗10^3, their sum is 5.26∗10^8. The sum equals the first addend.
How precise should I be?
Thinking about data in terms of decimal places is misleading.  You should really be thinking about data in terms of the precision with which you know the values, also sometimes referred to as significant figures.
How precisely do you actually know those values? It is 12.736% because you actually have enough data to say that it is accurate to one part in 100,000, or is it because of something like Excel defaulting to three decimal places?
You need to figure out the amount of error in your measurements, and once you know that, then the answer to your questions will be clear.