How do I round up a number to the nearest 1000 or round down to the nearest 1,000?

How do I round up a number to the nearest 1000 or round down to the nearest 1,000?

For example:

Round up the number 133,768  to 134,000   (nearest 1000)

Round down the number 133,768  to 133,000   (nearest 1000)

Thanks