The process of replacing a number with another number so that the last digit retained is unchanged if it is followed by 0, 1, 2, 3 or 4, or increased by 1 if it is immediately followed by 5, 6, 7, 8 or 9.
When rounding a number, we always specify the desired order of magnitude or position value ones, tens, hundreds, tenths, hundredths, etc.
The result of rounding is called a rounded number.
Example
When rounding the number 1234.56 to the nearest whole, we write 1235, because the digit that follows the ones position is a 5; this means that we must increase the digit in the ones position by 1 in the original number.