I have a series of floats that I want to round down to the nearest .25 below the float. I need them to always round down. For instance, 1.80 and 1.99 both need to round down to 1.75. I have a simple function to complete true rounding:

def rounder(x,y = .25):
    return y * round(x/y)

I want to modify this function so that it always rounds down, not just to the nearest. TIA.