gistfile1.rb

def site_taxes
    zones = Zone.match(self.shipment.address)
    tax_rates = zones.map { |zone| zone.tax_rates}.flatten.uniq
    calculated_taxes = {}
    tax_rates.each do |tax_rate|
      calculated_taxes[tax_rate.calculator.description] ||= 0
      calculated_taxes[tax_rate.calculator.description] += tax_rate.calculate_tax(self)
    end 
    calculated_taxes.delete_if { |k, v| v == 0 }
 end