However, making the same purchase via the Comixology website does not incur the same tax.Even if you do it on your iPad with the Safari browser.
Of course, it's not just that 9% that you're saving. There's 30% of the purchase price that would have gone to Apple. That is now divided between ComiXology and the publisher, in the publisher's favour.
Let's break it down.
A $0.99 comic costs $1.08 via the app. 8% of the customer's money goes to the government, 28% goes to Apple and 64% goes to ComiXology to be divided up between them, the publishers and creators.
However the same $0.99 comic costs $0.99 via the website, saving the customer money, and 100% of what they spend goes to Comixology to be divided up between them, the publishers and creators.
UPDATE: And yes, if your comic store has a digital comics storefront for ComiXology, that's a way to give them a cut too..