Showing Posts that contain a certain tag within a Category **fix included**

I have a client that is essentially wanting to use tags in parallel to Categories. Of course I advised against this practice however what the client wants, they get when possible.

So essentially they intend to use categories as their primary method of navigation through the site. And then when a user clicks on a tag link within the post, it will show all posts with that tag BUT only within the current category. Is this possible?

I know having the link show all posts with that tag is possible but I’m not sure if limiting it to posts within the category is possible.