def _buffer_box(bbox, interval):
    """Helper function to buffer a bounding box to the nearest multiple of interval

    args:
        bbox (list[float]): list of float values specifying coordinates, expects order to be [W,E,S,N]
        interval (float): float specifying multiple at which to buffer coordianates to

    returns:
        extent (tuple[float]): returns tuple of buffered coordinates rounded to interval in order of [W,E,S,N]
    """

    if bbox[0] % interval != 0:
        xmin = bbox[0] - (bbox[0] % interval)
    else:
        xmin = bbox[0]

    if bbox[1] % interval != 0:
        xmax = bbox[1] + (interval - (bbox[1] % interval))
    else:
        xmax = bbox[1]

    if bbox[2] % interval != 0:
        ymin = bbox[2] - (bbox[2] % interval)
    else:
        ymin = bbox[2]

    if bbox[3] % interval != 0:
        ymax = bbox[3] + (interval - (bbox[3] % interval))
    else:
        ymax = bbox[3]

    return (xmin, xmax, ymin, ymax)