To round a number to a particular digit, look at the digit immediately to the right of your target, in this case, the ones and tens respectively. If that digit is 4 or lower, zero it and everything to the right of it out. If that digit is 5 or higher, increase the target digit by one and zero everything to the right of it out. If your target digit is a 9, increasing it will turn it to zero and increase the digit to the left of it by one.
100
100
Zero
To the nearest 10 it is 980 To the nearest 100 it is 1000
It depends on the degree to which you are rounding: To the nearest integer: 99.5 To the nearest 10: 95 To the nearest 100: 50 To the nearest n: 100 - n/2
To the nearest 10: 2470 To the nearest 100: 2500
100
100
100
Zero
570 is the nearest ten. 600 is the nearest hundred.
100
83 rounded to the nearest 10 is 80.
To the nearest 10 it is 980 To the nearest 100 it is 1000
100
100
90