Swedish rounding (.45 up to .5) for Floats

swedish_rounding.rb

class Float
  # Public: Round a decimal number using the Swedish rounding system.
  #
  # This method complements Float#round but is intended for dealing with
  # currencies, etc. where a more 'real-life' rounding technique is needed.
  #
  # Basically, the vanilla Float#round method only looks at the first number,
  # which can lead to bad rounds.
  #
  # Example
  #
  #   4.45.round
  #   # => 4
  #
  # This method rounds more 'right-to-left' - that is, it yields the number
  # you would expect to gain from rounding this number if it was, for example
  # currency.
  #
  # Examples
  #
  #   4.45.round_swedish
  #   # => 5
  #   4.44.round_swedish
  #   # => 4
  #
  # Returns an integer
  def round_swedish
    ((self * 10.0).round / 10.0).round
  end
end