to round to the nearest ten you would look one place to the right from the tens place. if this number is greater than or equal to 5 you round up, if it is less than 5 you round down.
in this case the tens place is a 2, and to the right we have a 6 in the ones place.
6 is greater than 5 so we round up.
626 rounded to the nearest ten is 630