When it comes to Handango you must send all buyers back to Handango that downloaded your product from there. However it is recommended that you do <i>not</i> send buyers to Handango that downloaded your product elsewhere. You should instead use an online retailer like
http://eSellerate.com that charges a flat 10% commission, compared to Handango's minimum 30% commission. If Handango and others (PocketGear) want to claim that the high commission is for "exposure" and bandwidth / hosting fees that's fine. However that is all the more reason you should <i>not</i> send customers to Handango whenever possible, because they would be paid for "services" that you did not use.
More to the point of your question, I would recommend that you have a domain just for your product (like my DEXplor.com). Then in your About screen, (or Please Register screen), you could have something like this:
<b>To Register please go to mysite.com/handango</b> for your Handango build, or just <b>To Register please go to mysite.com</b> for your non-Handango build.
Then on your mysite.com/handango page you direct them to the appropriate Handango page to purchase, and on your default purchase page you send them to eSellerate, PayPal, or whatever your reasonable-commission (ie preferred) eStore is.
The beauty of this is that you meet the Handango requirement, yet if a customer gets lazy and goes to mysite.com instead of mysite.com/handango then you get to keep a higher portion of the profit.
The only real reason to send all customers to Handango for all your sales is if you want to try and buy a spot on Handango's Top Ten list (and I do mean buy, because it will cost you many thousands of dollars if you have enough sales to make it on the top ten list). PDAMill has done this very thing to dominate the top ten at Handango. I would speculate that easily the majority of Snails sales did not originate from Handango, considering the huge amount of discussion, reviews and awards the game has won. However PDAMill, for better or worse, has decided it is more important to let Handango have an extra $2 of every sale (assuming a 30% commission) in order to buy those top ten spots. Obviously there are very few other Top Ten spots left open to purchase in this manner, so for the other 99% of developers I would recommend you do not give Handango any money they did not earn. (sorry to go slightly OT about the Handango thing)
Dan East