Rounding of a number to nearest tenth or hundredth means we approximate it and for this we do not need a number beyod tenth or hundredth,
As we have in decimal number system, a number from 00 to 99 at a place,
if we have a number from 00 to 44, we remove the numbers beyond those desired completely - for example if a number is 3.141593.14159 and we need to round it to nearest hundredth, as we have 11 next to number in hundredth place, we just ignore it and write 3.143.14.
if we have a number from 55 to 99, we remove the numbers completely, but add 11 to the last desired digit- for example in the given case $21.38$21.38 and we need to round it to nearest tenth, as we have 88 next to number in tenth place, we ignore it but add 11 to 33, which is the last digit and rounding $21.38$21.38 to tenth place, it becomes $21.40$21.40.
