Tag Multiple Posts at Once

So, I had someone working for me who blew it in terms of post tagging. I.e., She was supposed to tag each post on my site like this: state name counseling internships

Instead, she sometimes tagged them: "state name counseling internship" (note singular)
and sometimes "state name counseling internships"

For a variety of reasons, I'd like them all to be uniform. They could either have both, or just one.

From WP-Admin, or via a plugin, or something, is anyone aware of a way to tag multiple posts at once?