How do you round a number to the nearest thousand?

If the last three digits of any number are equal to or greater than 500, then you round up to the nearest 1000. For example, the number 2573 rounds up to 3000.

If the last three digits of any number are equal to or less than 499, then you round down to the nearest 1000. For example, the number 2473 rounds down to 2000.

This assumes you are 'rounding up' which is the usual meaning of 'rounding'