When rounding, you need to consider what number come after the number you're rounding to. If the number after is greater than or equal to 5, you round your number up, and if it is less than 5, your number stays the same. In this case, 8 is greater than 9, so you round 9 up. Since you can't really have 10 as one decimal place, you need to round the number before up also. You get 20.00.
