def truncate(number, rounding_factor):
    """Truncate to nearest arbitrary multiple

    >>> truncate(1000, 100)
    1000
    >>> truncate(1099, 100)
    1000
    >>> truncate(1099, 50)
    1050
    >>> truncate(1099, 50)
    1050
    """
    return int(number) / int(rounding_factor) * int(rounding_factor)
