So I would like to give new customers a free gift on their first purchase and I plan on advertising this in print ads. The issue i'm having is, we are not allowed to give anything away (nature of the alcohol business here in NY where we're based). But I can charge people a penny. Is there a way for new customers to type in a coupon code, but instead of it subtracting money, it would add a penny. Is this doable? or something similar?

I saw a mod for free gifts (dangling carrots), but I don't like that it alters core files.