Excel, Formula, Self referential cell value, rounding a column?

Now I really hate MS! If I have a long column of numbers that I want to have rounded, either just displayed that way or actually changed, how do I do that? I would like to create a formula that says take the current number in the cell, and round it. How simple is that? Apparently I'll need to be a rocket scientist.
Oh.... Okay, I'm an idiot. I thought those display formats were just truncating. But I still hate MS.
Thanks!!