class Integer

def round_with_digits(ndigits=0)
  ndigits = Backports::coerce_to_int(ndigits)
  case
  when ndigits.zero?
    self
  when ndigits > 0
    raise RangeError if ndigits >= 1<<31
    Float(self)
  else
    pow = 10 ** (-ndigits)
    return 0 if pow.is_a?(Float) # when ndigits hugely negative
    remain = self % pow
    comp = self < 0 ? :<= : :<
    remain -= pow unless remain.send(comp, pow / 2)
    self - remain
  end
end