I gave a +1 to FumbleFingers and RedDwight for the most correct-yet-broad choices. But since you asked for a single word, I felt like posting this answer. You could shorten either of their suggestions to:
bar·gain -ing [bahr-guhn]
verb (used without object)
6. to discuss the terms of a bargain; haggle; negotiate.
see also: synonym: haggling
or
shop -ed, -ping
verb (used without object)
8. to visit shops and stores for purchasing or examining goods.
Both of these could refer to multiple acts of examining/negotiating-then-maybe-purchasing, but they don't have a strong connotation for that. Consider a not uncommon conversation:
I've been shopping all day.
Oh? What did you buy?
Nothing. The bargains weren't good enough.
There is another term, a recent neologism, that is creeping up in usage; it is still definitely in the realm of slang, but has a closer meaning to the single-word that you are looking for: sale-ing. I know its weak that the best reference is Urban Dictionary, but I have heard it used a lot recently without the prefix. Specifically like so:
I'm going sale-ing on Black Friday! Gonna shop all day and find some sweet deals.
I wouldn't use this word, except to make a pun. ("Oh your in the market for a new boat? I hope you get to go sale-ing!" I'm sorry.) But if you don't mind slang, you could try it out.