No one likes to see a cost of $11,126,342.43. Why are you showing it to the penny? Does it make or break the decision? Are you trying to show how exact you can be? Why are you showing the dollars? Same reason.
Same thing for percentages. Unless you are dealing in something highly exact and detailed there is almost never a reason to say 25.341% instead of just 25%.
Those extra digits have no impact on the information being displayed. When in doubt, round it out.