If we rounded 3 to the nearest tens, it would be 0.
Number 1 Rule:
If the number is above 5, round up.
5, 6, 7, 8, and 9
If the number is 4 and below, round down.
4, 3, 2, and 1
Since the number is 3, we have to round down to the nearest ten, which is 0.