cartridge order setup which adds in tax total

gistfile1.py

from decimal import Decimal

from cartridge.shop.models import Order, SelectedProduct


def setup(self, request):
    """
    Set order fields that are stored in the session, item_total, tax_total,
    and total based on the given cart, and copy the cart items to the order.
    Called in the final step of the checkout process prior to the payment
    handler being called.
    """
    self.key = request.session.session_key
    self.user_id = request.user.id
    for field in self.session_fields:
        if field in request.session:
            setattr(self, field, request.session[field])
    self.total = self.item_total = request.cart.total_price()
    if self.shipping_total is not None:
        self.shipping_total = Decimal(str(self.shipping_total))
        self.total += self.shipping_total
    if self.discount_total is not None:
        self.total -= self.discount_total
    self.tax_total = Decimal(str(request.session.get('tax_total')))
    if self.tax_total is not None:
        self.total += self.tax_total
    self.save()  # We need an ID before we can add related items.
    for item in request.cart:
        product_fields = [f.name for f in SelectedProduct._meta.fields]
        item = dict([(f, getattr(item, f)) for f in product_fields])
        self.items.create(**item)

Order.setup = setup