5 bites? Serious bites? If yes, euthanize it.

I have experience training military working dogs and there is very little that can be done to train it. De-training a military dog is not successful all of the time. There is a difference in de-training and training to get rid of aggression. How old is the dog? If it is not a puppy anymore, I'd say shoot it and be done.

There is a difference in bites. My German Shepherd, for example, instinctively used to nip at people to get their attention. He is programmed to do this. It took constant reinforcement to get this behavior to stop. He still does it from time to time as well. The trouble is that many cities consider this a dog bite and it goes against the dog. I mean, yes, it is still technically a bite, but this is why these are not one size fits all cases. He is muzzled every time we go out and he goes everywhere with me. If your dog is actually biting people, there is likely little that can be done. If someone claims to be able to fix it, it will not be cheap and results are not guaranteed. It is like trying to get a stupid person to use common sense; yeah, it is possible, but it goes against what they know.