Based on previous coupons, it varies by location.
In my area, it has to be $20 AFTER WALGREENS coupons/discounts. But it can get lower after MANUFACTURER's coupons.
It doesn't matter the ORDER you give the coupons in this case, even if you give them the $5 coupon first, if you go under $20 after Wag coupons, the register will AUTOMATICALLY add the $5 back on. The first time I tried to use one of these a few months ago, I had a cashier try and try to get the $5 to come off, but the computer automatically was subtracting it.
Also, its YMMV depending on cashier, manager, district manager, etc. Sometimes they make up their own rules.
Maggie