The reason for the heightened precision is quite fascinating. We have a base-10 numerical system. In base 10, there are only two exact fractions (1/2, or .5, and 1/5, or .2). Anything else you divide is going to have a trail of sticky digits attached. Think about it: You can't actually cut the price of something into perfect thirds; one third of a dollar is .333 (etc) cents. You've got to be sneaky and move a few pennies around to get to numbers round enough. On the other hand, it's easy to split an hour into thirds; it's an even 20 minutes. The Babylonians counted in base 60, which means that in addition to getting perfect fractions from multiples of two and five, they also throw three into the mix. It just makes division a smidgen more precise, because you're not rounding up and down as much.