This doesn't tally the price, but gives shows how to add pizzas to a order, and calculate the total amount, and access each one.
pizza_order = 
pizza_tally = 0
count = True
while count == True:
pizza = raw_input("What type of pizza do you want?")
if pizza != "":
count = False
print "You ordered ", len(pizza_order)
for p in pizza_order:
If you want to tally prices, it depends on how the pricing works. If every pizza is the same price, all you need is the length and the ability to multiply.
I have a feeling what you have in mind doesn't involve pizza's and this was an example.