Answer:
To give you an example:
I recently bought a tray of food from Panda Express. It came with a main dish, two side dishes (vegetable or meat), and a "free" fortune cookie. The total of this is $7.25 + tax. A large soda, which was added later, was ~$2.00 + tax. This brings the total to ~$9.25 + tax, or ~$12.00.
Of course, the example can be drastically different between the tax rate of your area, or what you buy.
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