Rules for Rounding

The standard rules for rounding a value are well known. But first, some definitions:

•   The most significant digit is the leftmost digit (not including leading zeros).

•   If you are rounding to n significant digits, then the least significant digit is the nth digit from the most significant digit. Note that the least significant digit can be a zero.

•   The first non-significant digit is the n+1st digit.

The rules for rounding are:

1) If the first non-significant digit is less than 5, then the least significant digit remains unchanged.

2) If the first non-significant digit is greater than 5, the least significant digit is incremented by 1.

3) if the first non-significant digit is 5, the least significant digit can either be incremented or left unchanged (see discussion on the right).

4) All non-significant digits are removed.