The following is the corporate coupon policy for Target stores.  I highly recommend printing out these coupon policies and keeping them in your coupon binder. 

Target Stores Coupon Policy

Coupons are a great way to save even more when shopping with us, and it’s easy to use them at our stores.
•    Target accepts one manufacturer coupon and [...]

The following is the official coupon policy from Walmart.   There are regional price differences between the Walmart stores so you should always check your Walmart store for price comparisions.   
Walmart Coupon Policy
Walmart accepts the following types of coupons (see guidelines below):

Manufacturer coupons (Cents Off)
Free merchandise (or manufacturer’s Buy-One-Get-One-Free) coupons
Store coupons
Pharmacy (Advertising and Promotional) [...]