Answer:
Look at your the second digit (tens digit), and if it is 5 and over, then you will round up to the next hundered. If it is 4 and under, you round it down to the previous one.
Explanation:
Example:
136 - you will have to round to the previous hundred making it 130.
The 3 in 136 is under 4, so you round down.
161 - you will have to round up a hundred, so your answer will be 200.
The 6 is over 5, so you round up.