In my opinion, when talking about a drug as potent as SD, 5 mg is ideal. I can guarantee you that there will be people who will want to take less than 10 mg at a time. It also provides the opportunity for more varied dosing.
But....if you're making tablets it doesn't matter too much because you can just break them in half. Regardless, I wouldn't dose your tabs over 10 mg under any circumstances. There are a LOT of people out there who do NOT want to take more than 10 mg at a time.