Do you pay your estimated sales/use tax for all items purchased online or out of state where taxes weren't paid? (Most people don't... although some states have a 'standard' amount you can claim if you don't know your actual, which does make it easier.)
If you aren't doing that- I wouldn't do this either. I've been told that people can get away with almost anything lately because there aren't enough employees to be doing many audits anymore, but this seems like a fairly rare deduction to take, so it would worry me it will cause a flag.
99.9% of it I pay state sales tax, as Amazon and most other companies I buy from online are based out of here or have an operation here.
I do recall reading an article where I believe this was a red flag for audit, since very few people do it, and the few who do it likely do it incorrectly. Too bad, I guess you'd almost be better off paying state income tax since it is easy to deduct, unlike itemizing hundreds if not thousands of receipts every year.
If it is worth a lot of money to you, and you are 100% honest and not "tricky" with anything else that is a potential flag or problem for IRS discussion, then why not?
An IRS audit for sales taxes is not going to be that tricky of a thing. You will get a couple of letters, be stressed about them for a couple of days, and then pay the amount they say is owing, unless you believe that they got it wrong. In which case you write back (with or without payment) with an explanation, and wait for another letter. There may be a penalty and arrears payment. That is the extent of your risk.
If you really think you have done the math right, and are complying with tax law, and the rest of your return is straight forward, I would claim it and see what happens.
If you are self employed, or claiming deductions "on the edge" of what is allowed, then it is not worth the hassle unless a great $ sum is involved, in which case you likely already have a tax accountant / attorney helping you.. :-)
And of course lastly, if it is a great sum for sales taxes... MMM has some great posts about enjoying the simple things in life, and building a quality experience of life that may interest you... :-)