It depends on whether you are rounding to the nearest integer, nearest 10, nearest 50 etc.
The smallest whole number that can be rounded to 500 is 450.
This depends what you are rounding 450 to. If its to the nearest hundred it's 500. If it is to the nearest whole number or tens place then it is 450.
You do nothing. 450 is already rounded to the nearest ten.
450
450
450 whole numbers.
The smallest whole number that can be rounded to 500 is 450.
Numbers from 450 to 549.
500
Any of the integers from 450 to 499 can be rounded to the nearest 100 as 500
500
450 to 549
453
500
450 to 549
450
500