How to uncache Commerce cart?

Question

In Drupal 7 Commerce, I am running into an issue with this workflow:

1. Add item to cart
2. Apply qualifying coupon. Correct discount is taken off item
3. Add new item to cart with qualifying discount.
4. Old discount in order shown UNTIL you reload the page 2 times.

Basically I am adding a coupon to the cart at the /checkout/% page

It seems like the block or view is being cached.

What is the best means to uncache the block?

I have tried using:

cache_clear_all('shopping_cart_summary_new', 'cache_views_data', TRUE); 

as well as:

$order_wrapper = entity_metadata_wrapper('commerce_order', $order);
commerce_coupon_commerce_cart_order_refresh($order_wrapper);