Since this site can’t publish Rav Avigdor Miller zt’l’s direct quotations, allow me please to paraphrase what Rav Miller said about this subject.
You’re sitting in the subway and a so-called blind man comes into the car tapping with his stick, and he’s peeking through his small glasses, looking for customers. He’s walking around and nobody is doing anything. So when he passes by, you just take out a penny – not a nickel, because this fellow is not worth a nickel – and you take that penny and drop it into his tin can. Don’t let anyone see that it’s only a penny, and you drop it into his tin cup with the most resounding bang that you can. And then lean back virtuously to enjoy the admiring gazes of your fellow passengers. Look, you have to do something, so you make it worth it.
When you’re waiting on line at the post office, and this gentile woman comes by. She’s knocking her pushka for veterans or cancer or some other gentile cause, so it’s good to always have a penny ready. Drop in a penny and she’ll give you a big thank you. And you’ve done what is required of you.