It's like buying a stereo. Put together a package of stuff and bargain. AS my Grandfather taught me, "If you don't ask, you cannot get." He was talking about women but it works universally.

I generally try to buy $100 or more worth of stuff 2 or 3 times a year. That way, when they see me coming they know they'll have a sale. I always ask "Is that the best you can do on this big purchase?" It's usually good for at least 10%.