Override TaxRate

tax_rate_decorator.rb

Spree::TaxRate.class_eval do

  attr_accessible :name

  # Creates necessary tax adjustments for the order.
  def adjust(order)
    label = create_label
    if included_in_price
      if Zone.default_tax.contains? order.tax_zone
        order.line_items.each { |line_item| create_adjustment(label, line_item, line_item) }
      else
        amount = -1 * calculator.compute(order)
        label = I18n.t(:refund) + label
        order.adjustments.create({:amount => amount,
                                  :source => order,
                                  :originator => self,
                                  :locked => true,
                                  :label => label}, :without_protection => true)
      end
    else
      create_adjustment(label, order, order)
    end
  end

  private
  def create_label
    "#{name.presence||tax_category.name} #{amount * 100}%"
  end

end