Rounding to nearest 100

Question

First number needs to be rounded to nearest second number. There are many ways of doing this, but whats the best and shortest algorithm? Anyone up for a challenge :-)

Answer 1

This will do it, given you're using integer math:

n = (n + 50) / 100 * 100

Of course, you didn't specify the behavior of e.g., 1350 and 1450, so I've elected to round up. If you need round-to-even, that'll not work.