how to round to 2 decimal ignoring any shit storage method in disk

round.py

"""
>>> round(2.5)
2
>>> round(3.5)
4
>>> round(4.5)
4
>>> round(1.555, 2)
1.55
>>> round(1.556, 2)
1.56

fees the brokers charging is rounded
due to the Floating-Point Arithmetic question, we actually will get the wrong allaways 
so, the code piece was written for the question

"""

def round_(number, ndigists=2):
    """
    desc:
        number   -> to rounding
        ndigists -> how many digiest to retained
    """
    value_str = str(number)
    whole_part, decimal_part = map(lambda x:map(lambda _: int(_), list(x)),
                                   value_str.split('.'))
    whole_part_hold = len(whole_part)
    decimal_part = decimal_part[:ndigists+1]
    decimal_part_hold = len(decimal_part)

    def addto(elements, position=-1):
        if decimal_part_hold <= ndigists
            return
        if elements[position] > 9:
            to_append, situ = elements[position]/10, elements[position]%10
            elements[position] = situ
            try:
                elements[position-1] += to_append
            except IndexError:
                elements.insert(0, to_append)
                addto.whole_part_hold += 1
            addto(elements, position-1)
        elif elements[position] > 4:
            if (addto.whole_part_hold + addto.decimal_part_hold - abs(position)) < (addto.whole_part_hold + ndigists):
                return
            if addto.upgrade:
                elements[position-1] += 1
                addto(elements, position-1)
            else:
                return
        else:
            return
    addto.upgrade = True
    addto.whole_part_hold = whole_part_hold
    addto.decimal_part_hold = decimal_part_hold
    todo_alice = (whole_part + decimal_part)
    addto(todo_alice, -1)
    whole_part = ''.join(map(lambda _: str(_), todo_alice[:addto.whole_part_hold]))
    decimal_part = ''.join(map(lambda _: str(_), todo_alice[addto.whole_part_hold: addto.whole_part_hold+ndigists]))
    return float(whole_part + '.' + decimal_part[:ndigists])