title: Bigcommerce API total cart calculation, payment
body: <p>I am very unhappy i can not find a work around to process these two calls.</p>
  
  <p>I would like to call the API with a json with all the data so that i can get a total cost of the cart. 
  Also i would like to call the API so that it will process a payment for an order created.</p>
  
  <p>Is there any way any of this sounds possible using any trick /hack / workaround?</p>