code: public void setSummary(String subtotal, String shipping_cost, String total_tax, String total_cost)
      {
          this.summary.put("subtotal", subtotal);
          this.summary.put("shipping_cost", shipping_cost);
          this.summary.put("total_tax", total_tax);
          this.summary.put("total_cost", total_cost);
      }
docs: Set Summary
  
  @param subtotal the receipt sub-total
  @param shipping_cost the receipt shipping cost
  @param total_tax the receipt total tax
  @param total_cost the receipt total cost