Hi Bert,
Thanks for reporting the issue with saving tax rates, I just tried playing with it and I do see some unexpected behavior. I will look into it.
Regarding the admin order entry, it like many things in WebStore are unfinished work, I threw that page together when I got a customer that wanted to pay by check with a PO and I needed a way to get the order in there so he could download. I implemented the minimum needed to accomplish that.
I "think" currently in the normal checkout process tax calculations are implemented only when processing payments directly like with Authorize.NET, I could be wrong and that may not be implemented yet either.
WebStore is really a work in progress in its very early stages, mainly I've implemented it as I go to support my own product sales needs but it made sense to share it and make it available for those with similar needs but it has a long way to go to be a general purpose ecommerce solution. I expect to make major progress on WebStore this year though.
Best,
Joe