Speaking from a GSA standpoint, half of the posts on this thread are actually sort of infuriating...
1) If you're going to the restroom "right before" you sit down for your break, that DOES count as your break time. If you need to go midshift, that's different; but if you're off a checklane at 12:04 because I sent you to break, even if you have to use the restroom during that time, you need to be back at 12:20. If it's "right before" or "Right after" your break, IT'S PART OF YOUR BREAK. Unless you're getting back on a checklane after you use the restroom, it's part of your break.
Edit: You have every right to use the restroom at any time... but drinking water, using the restroom, etc etc, aren't considered "work" and count as part of your break if you're on break. If you get sent on break at 12:04, and you sneak over to the restroom after that before you sit down, that is still part of your break and you should still be back at 12:20.
2) A fifteen minute break MEANS a fifteen minute break. Ie: 12:00-12:15. FIFTEEN minutes. Not 20. Not 25. Fifteen. "Not finishing your snack" does not empower you to add 10 minutes to your paid rest break. It's one thing to take a longer lunch (still not okay, but at least you aren't getting paid) but when you're on your employer's timeclock, you shouldn't be taking more than the Target policy and OSHA-regulated rest and meal breaks.
3) The GSA/GSTL will time every single break you take. We time every single break that the entire front end takes. Every day. Because we run the break schedule. We're supposed to know when you go to break, so we know when to expect you back. I don't know about anyone else on the forum; but I write down start-end times whenever somebody takes a long break, and if it becomes a pattern I hand those lists over to my GSTL per her request. She's done several coachings for people taking extra-long breaks.
4) When you take an extra 5-10 minutes on your break, you're making one of your fellow team members take their break late, too. It's not only affecting our guests, but you're making other people (who want their break just as much as you do) wait because a cashier decided they wanted to take a 25 minute fifteen. It's pretty rude to everyone else on the front end team who has to wait because you decided you needed another extra 10 minutes.
Our break room is right at the front of the store, and it takes 45 seconds AT MOST to get there from a register...
In regards to the OP: You can do whatever you want during your 15 minute break, as long as you don't leave target property (which can only be done on a 30 minute meal break where you punch out.) You can use the restroom, eat, shop, roam the store, call your mom, whatever your heart desires within those 15 minutes... If you do go out into the view of guests, Target requests that you take off your nametag. It's also a good idea to make it look like you aren't working. I like to keep my phone/wallet in my hand and take off my nametag. Wearing a sweatshirt (anything not-red) works well too.