Negative discount

Is there any way, using your app, for the client to press a button and get a "discount"? The reason I am asking is that if I can't get a 2 tiered quantity pricing, I am thinking outside the box. So if the client pressed a button they would get a negative discount. (For example $10 item now becomes $10.00 x 1.4 = $ 14.00)

I was thinking that I could use that as the "rush pricing"