It's definately tax deductible as a business expensive. If you are simply an employee then it generally isn't tax deductible. The 2% standard mentioned above may be correct but I can't verify it one way or the other.

When in doubt....deduct it! Worst case scenario you can be made to pay it back later. It's an interpretation of the law. You won't violate any laws. However, if you are in doubt about reporting income....report it! Failure to report your proper income is tax fraud.

Note: This post is for discussion reasons. Always consult competent professional advisers. I am not an attorney or CPA nor do I play one on the internet. I have, however, been running my own business since the age of 14.