By specifying the route as you are and specifying the controller you are in effect bypassing Sitecore. See section 4.1 of the Sitecore MVC Developers Guide
You could use Wildcard Items (section 1.2.6 of Reusing and Sharing Data document) to handle the tags, this would allow you to deal with the Item like any other Sitecore Item and add layout/rendering/rules etc.
You can find some relevant examples here: Sitecore MVC Music Store, it's a Sitecore 6.6 example but the concepts are the same still.
You could also take a look at the Wildcard Module but looking at the source code I'm not sure it will work with MVC since there is some WebForms specific code but it should be easy enough to modify.