You can also divide 10 by 2, 4 and 5 without getting infinitly long numerical expressions. In fact 12 is quite a waste, it's better to go with 6 because it has 2 and 3 as prime factors, thus also being friendly towards divisions over 4. On the other hand base 6 numbers are longer than base 10 numbers, so you need a lot of digits.
BTW: this discussion is quite off-topic. The choice for the number system base is quite different from the choice for the number of columns for a CSS grid.
http://www.youtube.com/watch?v=U6xJfP7-HCc
Mathematically, 10 is a pretty arbitrary choice to base your number system on. We would have been better off learning base 12 than inventing metric.