DTReg's tax display behavior isn't as good as it could be in my humble opinion.
My understanding of the current state:
a) EVENT LISTING: You can via a menu option confiure DTRegister to show the price both with and without taxes in the event listing. This isn't ideal because it never actually lists the taxes! I would like a user option to list (a) price; (b) taxes; and (c) the total (i.e. price + taxes). It would be even better if we could put the short description of the event through the tag parser! This would provide the ultimate in customizability and allow us to customize the site any way we'd like. It would also solve all kinds of preoblems unrealted to taxes and allow people so much customizability that they could conceivably use the same default messages for all their events.
b) EVENT SIGNUP FORM -- As far as I'm aware, there is currently NO SUPPORT FOR LISTING THE TAXES. The only thing you can do is to list the whole price including taxes which is not goof from a marketing perspective because the taxes in some countries is quite significant. I would be really pleased if we could turn off the built in price display and instead be allowed to pass the the "message to be displayed above event" field through the tag parser. This would provide us the ulimate in customizability to allow us to display the prices, taxes and totals any way we'd like.