What is 315 rounded too?

Answer 1

To the nearest 1 it is 315 - but that really isn't rounding

To the nearest 10 it is 320

To the nearest 100 it is 300

To the nearest 1000 (or any higher power of 10) it rounds to 0

Answer 2

The answer depends on the extent to which it is rounded. To the nearest unit it is 315 whereas to the nearest thousand, it is 0.