After the 99, the extra piece of a whole number is 0.49 .
Since that's less than 0.5, it's not enough to add 1 to the 99,
so the nearest whole number is 99.
Another way to talk about it:
You have 99.49 .
The next bigger whole number is 100. It's 0.51 away from 99.49 .
The next smaller whole number is 99. It's only 0.49 away from 99.49 .
99 is nearer than 100, so 99 is the nearest whole number.