If you can quarantine them without starving them or exposing them to copper and its not a major problem to you then sure, do it. However most threats to your tank will be in the water or carried by fish. As you have no snail eating fish (one would hope) the chance of direct parasite transmition is minimal. So you should be fine without, especially in a freshwater tank.
If you place the snails in a small bucket with the stores water then drip tank water into the bucket through a partially clamped airline to can acclimatise them nice and gently to the tanks water parameters. Once they're ready take them out of the bucket by hand, dip them in a jug of tank water and then put them in the tank. This should reduce the chance of anything from the shops tank water getting into your tank to near zero. Obviously dispose of the water in the bucket and jug, wash both out well and top the tank up again with fresh water.
Got four netrites from my LFS yesterday, 3 Bee staghorns and one I'm not sure what he is. Very interesting to see them exploring the tank and their little mouths eating away at the algae on the sides of the tank.
Nice one, I bought 5 bee staghorns and 2 Rubys. One of the staghorns has died and I have no idea why. Another was suppoed to be a staghorn but it doesn't look like one, it's more black and has a hatched texture with red tinges around the thin yellowish stripes. The staghorns are still babies and don't have a massive impact on the algae yet but I'm hoping they'll munch more when they grow up.
I don't bother quarantining anything other than fish. Usually I just do a quick rinse in some tank water, but maybe I'm being careless as I do have a quarantine tank set up most of the time anyway.