45,700
You either go up from 5-9 or down for 1-4.
Example:
56,891 to the nearest hundred.
An 8 is in the hundreds place so it will either be 56,800 or 56,900 depending on if you go up or down. Start at the ones place. The number is 1 so you take that down. Then you have 56,890. Next you go to the tens place. A 9 would go up so you then have 56,900. You are now in the hundreds place so you have solved the problem.