When you need to round a number. First you need to look at the placement number that the question is asking to round to the nearest.
In this case it's the nearest hundredths.
The 8 is in the hundredths place.
Now look to the number to the right of that number 5 that's the number that tells you if you will round up or down.
If the number is 5 or more you round up, if it's less than 5 you round down.
In this case it's 5 so you round up.
So your answer would be 18.99
Hope this helps.