In this lesson, students will use place value understanding to round decimals to the nearest whole. Round decimals to the nearest ten, hundred, thousand, etc., using a number line. Round decimals to the nearest whole using a number line. While students haven't rounded decimals to the nearest ten hundred, thousand, etc., they have rounded whole numbers to those place values. Rounding up a number results in a change in the value of the place to which youre rounding, where rounding down does not.