Round 256 and 321 ( need to when rounding in the hundreds place do we not change the entire number?

Is it a decimal? If you mean 2.56 and 3.21, they are 2.6 and 3.2 rounded to the nearest tenth. To the nearest whole number, they would both be 3.

If they are whole numbers, rounded to the hundreds place would be 300 for both. Rounded to two digits would be 260 and 320, respectively.

Please clarify what you mean.