Let someone go first

lady behind me had a couple cans of soda and a lunch meal while I had about 25 items in my cart. Saw her walk up and do the math on how long it'd take to get out of there. Before she had time to really saw it do anything I smiled and said "go in ahead of me" got a great smile in return and she paid and left. Thinking this isn't just an act of kindness, this should always happen.