What is the main difference between using the ROUND function and using number formatting to make all values appear as
whole numbers without decimal places?
The ROUND function allows a user to choose a certain number of decimal places that will be shown in the cell, but when
number formatting is used, numbers are always changed to whole numbers.
The ROUND function always changes numbers to whole numbers, but when number formatting is used, the user can
choose a certain number of decimal places that will be shown in the cell.
Using the ROUND function changes the value so that the rounded value is used in other calculations, but when cells are
formatted as whole numbers, all digits after the decimal are still used in other calculations.
Using the ROUND function changes the appearance of the value (all digits after the decimal are still used in other
calculations), but when cells are formatted as whole numbers, the rounded value is used in other calculations.

Using the ROUND function changes the value so that the rounded value is used in other calculations, but when cells are formatted as whole numbers, all digits after the decimal are still used in other calculations.

Explanation:

When we round a function then the rounded value is being used in all the calculations. And you should not that when we format a number to a certain number of decimal values, then it shows that many numbers on the screen, however, the actual number is used during all the calculations, and not the value that is displayed on the sheet after formatting. Hence, the above option is the correct option.