Odd "discount"

I saw a message on Twitter earlier today pointing to this offer by Dusty Schmidt through his affiliate site. Black Chip Poker is part of the Merge network, which appears to be the largest U.S.-facing site left (assuming that you don't want to give your money to the thieves at Cereus). Good rakeback plus Schmidt's three e-books (I have been wanting to read Don't Listen to Phil Hellmuth, but had balked at the purchase price) seemed like a good deal to me, so I signed up, deposited $100 on my Visa card, which went through without a hitch. (Merge also has Mac client software, for those of you to whom that might be a deciding factor.)

I got this strange email from Black Chip soon thereafter:

"Your $100.00 Black Chip Poker Visa deposit has been approved. Please be aware that we have given you a discount on this transaction, in the range of 1 - 5 cents. You will still be credited the full amount of your deposit, however, you will be billed slightly less."

When I got the notification from the payment processor, the billed amount was actually $99.93.

I can't figure out the reason behind this. I don't think it's an artifact of foreign exchange rounding. I wonder if it's an attempt to slightly randomize the deposit amounts. I assume that $100 is a very common starting deposit, so maybe they think it will attract less scrutiny if there are not a whole bunch of transactions of precisely the same dollar amount.

Theories, anyone? Speculation? Informed answers?