What is a definition of rounding numbers?

Answer 1

It means that you find the closest whole number. For example, if you have the number 5.8, rounding it to a whole number gives you 6 - since no other whole number is closer to 5.8.More generally, it can mean rounding to some multiple of a certain number. For example, 549 rounded to the nearest 100 (i.e., to the nearest multiple of 100) gives you 500 - since no other multiple of 100 is closer to 549.

Answer 2

altered for convenience of expression or calculation