To express a number as a higher or the next-highest number, especially so as to eliminate decimal places in a non-whole number. (Usually done when the non-whole number is .5 or greater; lower than that, and the number would typically be rounded down.) A noun or pronoun can be used between "round" and "up." Most stores mark their prices at .99 instead of rounding up to the nearest dollar. The accountant had been using the exact numbers from the sales data, while I had been rounding them up to whole numbers when doing my own calculations.