I've hidden tagged photos or posts from my timeline, but people can still see them.
When you hide a photo or post you're tagged in on your timeline, or adjust your timeline and tagging privacy setting, this only limits who can see the content on your timeline. The photo or post is still visible to the audience it's shared with other places on Facebook, such as in News Feed or search.
Please keep in mind that the person who uploaded a photo chooses the audience for that photo. If you're tagged in something you don't like, you can remove the tag or ask the person who posted it to take it down.