It depends on what you're doing.

If you're an office worker with no hands-on hobbies and hands soft like a baby, then, no, you don't need a tetanus shot. Same if you don't have pets that walk in mud and dirt and then scratch you (I mean farm dogs and stuff, not city pups who get bathed at least once in a while.)

If you're a farmer, construction worker, or anyone else who has a high chance of getting a dirty scratch (it isn't just "rusty nails"), you might want that top-up every so often, just to be sure. Lockjaw sucks, I've known people whov'e gotten it.