def secToHHMMSS(seconds):
    """
        Converts input seconds into the desired output display format.
        Rounds to the nearest second.
    """

    rndSec = int(seconds + 0.5)  # rounded seconds
    
    hrs = int(rndSec / 3600)
    min = int((rndSec - hrs * 3600) / 60)
    sec = rndSec - hrs * 3600 - min * 60
    
    return str(hrs).zfill(2) + ":" + str(min).zfill(2) + ":" + str(sec).zfill(2) + ".0000000"