Silver Dollars would be way too large for a 10 gallon tank anyway. If you already have 5 tetras, just get more tetras because you don't have much space to add some larger fish. Besides, tetras are happy in schools so if you add more tetras, they'll be happy
Do you know what is the adult size of Black Skirt and Buenos Aires tetras? When I said that you can add more tetras to your tank, I've assumed Skirt tetras and Buenos Aires tetras don't grow large. If they do, you may have to stop right there.