I've noticed that if I've set transaction fees to 0.00 in my preferences and config file, when I try to send
bitcoin via the GUI, it sometimes prompts me if I want to pay a transaction fee of .0005 and sometimes
doesn't prompt me and sends with no transaction fee. I have the following questions:
1) Why does it only prompt me sometimes and on what does this depend?
2) I've noticed that when I make the call to sendfrom via the JSON-RPC API, I don't get prompted. It will just
assume I want to pay the .0005 transaction fee. Is there a way to get notified of this from the API before
committing to sending? Is it capped at .0005? Could it ever be higher than that? Is there a way to override
the GUI preferences and the config file settings and choose a specific transaction fee via the API and have
the call fail with an appropriate error message if the transaction fee is too low?