This is a great question. You may not deduct the cost of the wedding from your income. However, as you mentioned, there is a sales tax deduction if you itemize deductions. (This deduction will only be available for tax year 2007 unless Congress agrees to extend it).
You are allowed to either deduct an "optional" sales tax amount using tables provided in Pub 600, from www.irs.gov, or deduct your actual sales tax. In order to deduct your actual sales tax, you need to keep receipts showing the amount of sales tax paid. You can deduct all sales tax on purchases for the entire tax year, and in NY, NY, this can be quite a lot, especially if your wedding package and services are all taxable.
Please keep in mind that you must itemize deductions to receive this benefit, and your sales tax deductions needs to be greater than your state and local income tax deduction in order to really benefit (since you may choose between sales tax or income tax deduction).
If you have additional questions that you can't find answers for in Publication 600, let me know!!!
Do you any other question? Did you get the information you need?