Commissions - How do you calculate and play them

I'm having a little trouble understanding commissions, and how it will affect my automated scalping strategy that I'm currently building.

Say spread is 1 pip. I'm trading 1 minilot, 10K, on eur/usd. Pip value = $1. Price is currently 1.5629.

So commission would be 1.5629 X 10000 X .00005 (I'm on MBT) = .78415. That means round trip would be .78415 X 2 = 1.5629. Interesting how that equals price. Is that the quick way to calculate commission?

Anyways, so spread is $1. With commission that totals 2.5629. Essentially I need a 3 pip profit to break even correct?

Whats the best way of automating a scalping strategy where spread and commission are so variable? Do I just play it to assume I'm playing a currency with 3-4 pip spread?

I'm not sure if this will help me or hurt me. Say I enter a trade with 10 TP 10 SL. With the commission charges coming at the end and not actually in pips, I am 11 pips away from my TP and 9 away from my SL. So the trade is more evenly balanced even though I'm playing it as if I was 13 away from TP and 7 away from SL. I guess it helps my trades have a better chance at TP if the cost is taken off at the end. Or should I really be increasing my TP and decreasing my SL to compensate for the commission?

Whats the best way of attacking this matter in an API? Assume the spread is a set larger figure?

You are correct that the round trip equals a pip value, as you suggest I just tend to regard this as part of the spread. As for calculating commissions, I believe that there is an example somewhere MB API documentation (or it was on the news group). Be aware however, that MB (and EFX) commissions are crap, I would not use them for scalping.

Yea I understand. I'm using MB to test the system. If it works and grows the account to $7500 or $10K I'll be switching to one of the other ECN's quickly.