The decimal 82.2 is 82 when rounded to the nearest point.
rounded to 1 decimal place it is 24.7
Any decimal less than one will round to zero.
34.67, rounded to the nearest decimal point, is 34.7.
It is 0.0 : the zero after the decimal point is an indication that the number is rounded to the nearest tenth.
2.75590551 rounded to the nearest tenths (its one place after the decimal point) is 2.8.
That's rounding to two decimal places. When rounding to a specific place, take a look at the digit immediately to the right of the target, in this case, the thousandths place. If that digit is 4 or less, zero everything to the right of the target out. If that digit is 5 through 9, increase the target by one and zero everything to the right of it out. If the target is a 9, increasing it will turn it to zero and increase the digit to the left of the target by one.
The thousandths place is the third digit after the decimal point. 86.255 only has 3 digits after the decimal point so it is already (possibly) rounded to the nearest thousandth.