|How is the number getting into the cell?|
Assuming it's the result of a formula, I'd try this.
I'll use =A1+B1 as the "base" formula for getting the number in the cell.
P.S. you didn't say what should happen if the decimal is < 0.5, so I don't know if you always want to ROUNDUP or just ROUND the result.
I assumed ROUND.