The ROUNDUP function rounds a number up to a given number of places. The number of places is controlled by the number of digits provided in the second argument (num_digits). For example, these formulas round the number 5.13 up to 1 and zero places:
=ROUNDUP(5.13,1) // returns 5.2
=ROUNDUP(5.13,0) // returns 6
In the example, the formula in cell D7 is
This tells Excel to take the value in B7 (PI) and round it to the number of digits in cell C7 (3) with a result of 3.142 Notice that even though the number in the 4th position to the right of the decimal is 1, it is still rounded up to 2.
In the table, the ROUNDUP function is used to round the same number (pi, created with the PI function) to a decreasing number of digits, starting at 4 and moving down past zero to -1. Note that positive numbers round to the right of the decimal point, while digits less than or equal to zero round to the left.
You can see that ROUNDUP is a rather heavy-handed function, so use with care. You can use the CEILING function to round a number up to a given multiple. If you want to discard the decimal portion of a number, you can use the TRUNC function.