nathan 7372 (3/2/2010)
Thats the funny thing about decimal places. Technically, you are both right. Obviously Jeff's higher precision datatype leads to a more mathematically accurate answer. At the same time however, accounting is looking at having me calculate it with as little as 2 decimal places in order to save money. When all of those decimal places get truncated the company saves. So really precision has more to do with business requirements than it does with getting the "right" answer. Just food for thought.
After chewing on this "food for thought", I think the accountants may be right. Although you certainly want to use as high a precision as possible in calculations, the fact that the result is paid monthly means it should probably be expressed and saved rounded to two decimal places. The next month's calculation should use that actual monetary value as a base, not an imaginary 12 decimal place figure.
It's not about shaving fractions for the company's benefit, but about accurately representing the real value of the account. You wouldn't cut a check for $354.395840049589, so why would you say that's the balance at the end of July?