for awhile (about a year) i barely paid anything for my old spice body wash/deodorant + random things like toothpaste and floss..
at london drugs yoy can coupon stack as long as the coupon is for the same product and has a different barcode..
so for example if you had a coupon for $3 off if you buy 2 bodywashes.. and you have a coupon that says $1 off one bodywash.. you can use one of the $3 coupons and 2 of the $1 coupons
and sometimes online sources of coupons will give you the exact same coupon as the printed flyer source.. (but different barcode!) so that's 6 coupons for 2 items.. you still have to pay tax, and some coupons state you cannot stack.. so read the rules to avoid embarrassment
happy couponing
i stopped though.. cuz its a pain in the pass to collect them