Answer:
0 or 256.000.
Explanation:
Why 0? If you round 256 to the nearest 1,000, it will give you 0 because as the rounding rule says is the digit is greater than 500 it rounds to up, but if the digit is less than 500 it rounds to down. But as 256 is less than a thousand and less than 500 it equals 0. If you put this title: rounding calculator, you can prove that my answer is correct.
Why 256.000? If you round 256 to the nearest thousands (3 decimals), it will give you 256.000. My explanation: because when rounding numbers that are less than needed it adds the decimal place from left to right. ( the answer is correct but the explanation may not be ).
Hope this helps.