Young minds sometimes grapple when trying to figure out which digit needs to be rounded off in a rounding numbers exercise. Rounding is a necessary skill for estimating. When you ask a child to estimate something, you learn a great deal about the understanding or lack of it merely by asking. A child who makes an outlandish estimate really doesn't have a sense of understanding of the underlying concept. The child who makes a good estimate usually does. Here are a few things to help young learners out with the process of rounding numbers.
See also the Rounding Numbers Worksheets.