I've had the same experience all over the world - cab drivers claiming they have no change. It's very annoying! One would think that's part of their job. I've had some cabbies drive all over just trying to find change. So I try to bring what I think is the correct amount with me to avoid unpleasantness and delay. Doesn't always work. I lived for years in New York, so the idea of a crazy driver doesn't surprise me.
Mandi