Things that don't work: Multiple Tax lines, DHL plugin, more. I tried searching their forums for answers but there's nothing there. No chance I'm paying to get a simple answer.
The idea of releasing a component loaded with problems and charging to explain how it works is a joke. Take some time to make some support documents and maybe the community could actually get behind this product.
Just to clarify - we never charge just to ask a question about a feature. You're welcome to ask about features in our support center (no subscription needed for pre-sale questions).
Also - we now (in 0.9.0) have the ability to handle Canadian taxes (and any location that requires compound taxes).
DHL shipping is still in progress. Unfortunately we've not had a lot of people request this (feel free to let us know if you'd like to see the DHL shipping system functional for Tienda and we'll get on it).