I knew what I needed to do. I said to the cashier, "I'll pay for his lunch." The guy was stunned. He was speechless for a second, and then said "no, no, you don't have to do that". I could tell he felt awkward accepting my money, so I told him that this was an act of kindness and he was helping me get to my goal of 26. After that, he accepted my offer. :)
He was so appreciative and told me twice that he would pay it forward. I have no doubt that he will!