I never spend more than $0.10 on transaction fees for bitcoin. I mean, you could give $5 if you wanted to, but why would you? If I was sending a dollar I wouldn't pay more than $0.01 or less for the transaction fee. And for something so cheap the merchant shouldn't bother waiting on confirmations. Exploiting 0 confirmations isn't easy, and it's not worth the work to anyone for a dollar. Even with sub cent transaction fees they'll still settle faster than 3-5 business days.