For some reason, possibly because they think they are obliged to give, many people look away when asked for change. The message this probably sends is 'I couldn't give a fuck about you' rather than 'I feel guilty at my lack of charity'. The best compromise is either:
- Look at the person and say "No", but in an apologetic tone of voice.
- Give them some change.
Saying 'No, sorry' always suggests (to me at least) 'I have change but I don't want to give it to you' rather than an intended 'I genuinely can't spare my change, but I feel bad about your lifestyle'.