How+to+round+numbers

Rounding Numbers
 * Rounding makes numbers that are easier to work with in your head.
 * Rounded numbers are only approximate.
 * An exact answer generally can not be obtained using rounded numbers.
 * Use rounding to get a answer that is close but that does not have to be exact.

How to round numbers

 * Make the numbers that end in 1 through 4 into the next lower number that ends in 0. For example 74 rounded to the nearest ten would be 70.
 * Numbers that end in a digit of 5 or more should be rounded up to the next even ten. The number 88 rounded to the nearest ten would be 90.