a daily multi-vitamin

If you are using a good quality food, I don't see the point.  In fact, I can see it being more harmful.  It could cause overdoses of certain vitamins.

Daily vitamins are a personal choice I personally don't use them.  For most dog vitamins they use synthetic vitamin E and that is a waste of money...synthetic vitamin E is dl-tocopherol.  Your dog should be getting most required vitamins required from food.  If you include fresh raw foods your dog will be getting natural vitamins not destroyed by heating.[]

I give some fresh and or dried herbs for natural vitamins, fruit/berries for vitamin C as it is detroyed in the heating process...and I'm not a big fan of just partial components of vitamin C...I like it in it's natural form.  Vitamin E, I give a supplement every few days of just Vit E with d-alpha tocopherol (which is natural) & I make sure it has all 8 components including alpha-, beta-, delta-, and gamma- tocopherols.

This is just what I do for my dogs.  It's working great for them.[]  

I give Ginny a multi once a week - I don't see much point in daily dosage, plus the overloading that can come with it. However I am a hypocrite cause I take a multi every day

I've been considering a daily mult-vitamin because I feed raw.

Any raw feeders strongly suggest a daily mult-vitamin.

As for vitamin-type supplements that I give her daily: Fish oil, 200 I.U.'s of non-synthetic vitamin E, sea kelp.
I normally add a couple spoonfults of carrots or green beans to her yogurt.