Commerce Coupons, Discounts, and Tax not appearing on Checkout Review page So I'm able to apply coupons on the Checkout page. Quantity-based discounts also appear on the Checkout page. As does basic state-based Sales tax. But, when you continue from there, you select a shipping service, and then continue to Checkout review. At this point, the coupon is gone, as are the discounts and tax. 

The coupon entered still appears in the form, but the Granted Amount is now $0.00. 

I'm losing my mind on this one because I'm dealing with a site that is (was) 95% complete when this started happening. I must have introduced something stupid along the way.
Solved! Rules was the culprit. By rolling back to the previous stable version, all of the problems with checkout disappeared. Everything applies correctly to the Checkout Page, and is still there when I get to Checkout Review. 

Just to be clear, I replaced the current stable version of Rules (7.x-2.8) from January 2015 with the previous stable version (7.x-2.7) from May 2014.