A nice clean number is considered to be "round". What does that mean? Well, it depends. For the age of a person, 50 is a nice round number, as is 30. Actually, any number can be considered to be a "round" number. You see, this is not a precise scientific term. Though it has no precise meaning, fractions are never considered to be "round" numbers. You can think of all whole numbers as being round (1,2,3,...) if you want. "Rounding up" means moving up to the next round number, whatever you want that to mean. Often, it means the next whole number so you would round 3.27 up to 4. You could also "round it down" to 3. If you rounded 185 up to the next multiple of 50, it would take you to 200. If you rounded down, it would take you to 150. In sum, "rounding" has no precise meaning unless you specify what you mean by it, and that can vary.