taxes.rb

require "bigdecimal"
class Receipt
  def initialize
    @items = []
    @total_tax = BigDecimal.new(0.0,2)
    @total_cost = BigDecimal.new(0.0,2)
  end

  def add(item)
    @items.push(item)
  end

  def total_cost
    @items.each do |item|
      @total_cost+= item.price
    end
    @total_cost.round(2).to_s("F")
  end

  def total_tax
    @items.each do |item|
      @total_tax+= item.tax_calc
    end
    @total_tax.round(2).to_s("F")
  end
end

class Item
  attr_reader :name, :quantity, :cost
  def initialize(name, quantity, cost)
    @name     = name
    @quantity = quantity
    @cost     = BigDecimal.new(cost,2)
  end

  def price
    quantity * cost
  end

  def tax_calc
    price * tax_rate
  end

  def tax_rate
    case name
    when /Imported Bottle of Perfume/i, /Imported Box of Chocolate/i
      BigDecimal.new(0.15, 2)
    when /Bottle of Perfume/i, /Music CD/i
      BigDecimal.new(0.10,2)
    when /Book/i, /Chocolate Bar/i, /Packet of Headache Pills/i
      BigDecimal.new(0.00,2)
    end
  end
end

receipt = Receipt.new
receipt.add Item.new("Book", 10, 5.50)
receipt.add Item.new("Bottle of Perfume", 1, 95.00)

puts "Sales Taxes: " + receipt.total_tax
puts "Total: " + receipt.total_cost