If your total is a Decimal Field set to two decimal places, that should take care of it for you.
Here's my solution. (The field nfTotal has the settings pictured above.)
Side note: If you just wanted to test to verify that you'll get the right answer when rounding using a decimal field, create two decimal fields--one with two trailing digits and the other with three. Set the calculate script of one with two decimals to copy the rawValue of the one with three decimals.