I threw five dollars in the salvation army bucket and the woman said 'god bless you'. I told her' I'm an atheist. But I still try to help people out'.

I always go with #1. But politely. No thanks. I'm an atheist. Since I've been openly atheist I find it important to be unfailingly polite as to not give atheists a bad reputation. In this tiny area I'm the only one they will probably ever meet.

I can tell you were so taken aback about her being a "christian" and not someone who wanted to flirt with you. What a bummer.

Several years ago my niece and her family from Texass came for a visit. They are Jehovah's Witness.She did try to proselytize once but on the way home I lost her on the ferry. Later I found the family sitting with a bunch of other Witnesses. It is illegal to openly proselytize on the ferries so these people sit with a sign saying something (how to get world peace) and let suckers come to them. I have taken hundreds of ferry trips and have never seen these people. Now, on my trips I see them often. Once, the boat was almost empty and a woman who was at her spot came over and stood in the space in front of me. She was looking out the window and every once in a while she would look at me. I didn't bite and kept on reading. She finally left.

Yeah, I always think of something clever and biting to say after it's too late.
Usually, I just say something like, "no thank you - I'm not interested."

Each of the possible 5 answers is perfectly appropriate.

All you needed to say is, 'No I don't' The end. No explanation required.

I prob would have given the same answer as I rarely have cash . But I would have like you wanted to say much more. Good restraint gotta be careful about that BP.