Grip
You use your fingers in a shop to grip what you want to buy.
Imagine picking up a few different things in a shop. If something fits nicely in your grip: buy it. If it's too small or too big, put it back.
あく
にぎ
None
You have a really strong grip thanks to acupuncture (あく)! All your fingers are primed for buying things. You can grip anything at a shop—pineapples, tires, even live turtles. All thanks to some well-placed needles.
Acupuncture is great for strengthening your grip strength. If you do intense shopping (like I do) you should definitely consider it!