Break ins are very common on the Island. There are signs at all of the tourist attractions to not leave anything in your car, not even a bag with garbage because the thieves don't know that it is garbage. Any local will tell you the same thing. Anyplace that has tourists is going to be a hot spot, no matter where you are. The trunk is not safe either. Not only does your stuff get stolen, but then you have to deal with a broken window.
While we have never had a break in on any of our trips to the Hawaiian islands, I know it happens so like @Lilsia says, we never leave anything in the car.
I think logically the odds are greater if you are off the beaten path versus the Target parking lot but I know it happens everywhere so we practice caution.