Let's stop and think about a calulator for a minute. Would you use one that only had a scale of 4 decimal points? Probably not. Would you use one that did it's calculations in binary and then returned it's answer in decimal knowing that certain decimal numbers have no binary equivalent within the scale of the calculator? Probably not.

For Multiplication and, certainly, Division on "money problems", do what any decent $3.00 calculator does behind the scenes... do the calculations in Decimal with at least 15 digits to the right of the Decimal Point and don't convert to a two Decimal Place number until you actually want to display it. For mortgage calculations, I'd never store just 2 Decimal Places either. Spreadsheets don't. They just display the answer with 2 Decimal Places unless you make the huge mathematical error of rounding such things.