Am I Miserly Liar?

Within the past week, I have been asked on the street by three separate people for "change" or "fifty cents." Each time, I have had fifty cents, but I have shaken my head and said "sorry." I feel an overwhelming sense of guilt each time. It is not that I don't want to give some money - and in other cases, I have given money to people who have asked me. But, in each of these cases, I haven't felt safe. I am walking somewhere, by myself, already gripping my pepper spray in one hand, and I don't feel comfortable coming within arms reach of a strange person on a street corner. What is the moral imperative here? Clearly, as Christians, we are supposed to help people in need. And if you are reduced to asking for change on a street corner, you are clearly in need. I don't know how much of that need fifty-cents will fill, but that is what they have asked for. I still don't know what to do.