How to patch small holes in concrete slab basement floor?
You can use a variety of patch products. 

Premixed concrete patch would work. 

Platinum patch 

Vinyl spackling 

For holes that small i would use the vinyl spackling. You can sand it down if you are sloppy in the application. 

I would not worry about holes smaller then a nickle or dime. 

Clean and vacuum the holes out to insure good adhesion.