With my accounts I have with a broker he calls around and tries to get me the best price and his commisions are reasonable
For my retirement accounts with T Rowe Price Schwab and Fidelity I use the pink sheet US OT BB (or whatever you call it) symbols
Fidelity and Schwab screw me on the commissions for the very low priced stocks but are much better as the price increases. With them I often also seem to lose a penny or two in the transaction.
So for the little ones I just use my broker. For stuff like NEM.V and SRM.V I can just barely get away with buying them with the computer