Well the shingles butt up pretty snug so on the vast majority you do have to lift a tab to see the nail. on some where they are not butted so tight against one another you can see the nail between the the two shingles.
Greetings, I have a new GAF 30 yr roof. Have about 100 nails exposed under the seams of shingles. Roofer says no worries it won't leak. I think sooner or somewhat latter it will.