Whole numbers have no decimal numbers after them, so your two choices are 4 or 5. When rounding, decimals below 5 round down and those above 5 round up, so your answer should be 4.
141
421 rounded to nearest tens is 420
420
420
400
400
42.1
420
400
Any multiple of 421
It is 400 rounded to the nearest hundred.
420
420