How to round to the nearest dollar add or subtract

Okay Abrahammontiel1, the thing you must remember is any thing that is 5 or over must be rounded up and anything lower must be rounded down.
Example:
$2.30
since we want to round to the nearest dollar we look at the digit behind the whole dollar, which in this case is 0.3
and since it's lower that 0.5 we must round down
So it will look like this: $2

If we had a number like $4.72
we would look at the 0.7
and since it is greater that 0.5 we would round  up so that it would equal $5

D; 15

Step-by-step explanation:

Because the highest point on the graph is at 15 (or 3 am), that would be the highest temperature. (Also, none of the other choices make sense; they are all at relatively low temperatures).