I don't think coffee grounds would hurt the chickens but you should probably ask a barista at a Strawbucks for expert advice.
Just kidding about the barista!
My chickens eat Habanero Peppers and don't seem to be bothered by the capcacin/heat in the peppers so I doubt coffee grounds would hurt if they ate a few. Heck, chickens eat pebbles so I really wouldn't worry about it.
And as others have mentioned, coffee grounds are great for the compost pile or directly in the garden.
My compost bin is totally in my chicken run. They love eating all the nonsense I throw out there -- and they leave what they don't like. I don't put out any meat or avocados and my bread scraps go straight out instead of sitting in a compost bin to get moldy. They also don't get anything I wouldn't give my dog.