When you round off a number, always check the number that is located at the right side. WHen that number is 5-9, round up. But when it is 0-4, dont change the number. 
For example,
164, round to the nearest tens.
The tens is 6 and at its right side is 4, so dont change the tens digit. The answer is 160.

But when you say 'round the nearest hundreds then the answer will be 200. Because 1 is in the hundreds place and beside it is 6 so round up. 
It can be 525 or 526 or 527 or 528 but since you're lookng for the LARGEST, then the answer should be 529