Rounds an array up to N digits from the left, taking the element with more digits to the left ['max(abs(x(:)))'] as the reference. So, it is different from ROUNDN (mappinf toolbox) because this latter takes the dot as reference.
roundd(0.012345,3) = 0.012300
roundd(0.012345,4) = 0.012350, etc

Note: inside there is a function that check where an array has integer (natural numbers) elements: ISNATURAL

Check the screenshot for an example.