You can stop Excel from rounding large numbers by changing the cell format from General to Number. This trick works for numbers containing 15 or less than 15 digits.

How to Stop Rounding in Excel. When you import, enter or paste sales figures, salaries or other numeric data about your business into a Microsoft Excel worksheet, ...

Open your business spreadsheet in Microsoft Excel. Locate the cell that needs rounding up. As an example, "A1" may contain your calculation. Enter "Roundup(A1,-1)" without quotes in any empty cell.