how can i round each number to the place of the underlined digit?

Answer 1

An underlined digit usually means that the digit is significant, and in general, it is a trailing zero, i.e. a zero at the end of a number. Most of the time there would be no more digits following the underlined digit.
Could you post an example of the question you are trying to do?

Answer 2

You need to round the number that is underlined