In regards to grapes & raisins - they are toxic to the kidneys of dogs. Even if a dog doesn't get sick right away from eating them, like a classic case of poisoning, the damage will show down the road in the impairment of kidney function in later years.
Avoid biting when a simple growl will do
The Spirit Lives As Long As Someone Who Lives Remembers You - Navaho Saying
Vindication ~ For all those pets who became sick or lost their lives from tainted pet food