How to round a integer to the close hundred?

Question

I don\'t know it my nomenclature is correct! Anyway, these are the integer I have, for example :

76
121
9660

And I\'d like to round them to

Answer 1

If you only want to round integer numbers up (as the OP actually did), then you can resort to this solution:

public static class MathExtensions
{
    public static int RoundUpTo(this int number, int nearest)
    {
        if (nearest < 10 || nearest % 10 != 0)
            throw new ArgumentOutOfRangeException(nameof(nearest), $"{nameof(nearest)} must be a positive multiple of 10, but you specified {nearest}.");

        int modulo = number % nearest;
        return modulo == 0 ? number : modulo > 0 ? number + (nearest - modulo) : number - modulo;
    }
}

If you want to perform floating-point (or decimal) rounding, then resort to the answers of @krizzzn and @Jim Aho.