Not technically grape shot, but canister shot. Grape shot was pretty much absolete by the time of the Civil War.
I too found a small cannon ball or “grape” or “canister” shot as you both call it. Looking on the internet I saw it identified as grape shot, but know very little about the history of cannons, so won’t argue with anybody!
I literally stumbled over it in a field that was being prepared as a parking lot. I thought I had kicked up a geode, but when I picked it up I knew right away what it was.