You can deduct any expense that is considered ordinary and necessary, and that certainly includes business taxes you have to pay.

To be deductible, a business expense must be both ordinary and necessary. An ordinary expense is one that is common and accepted in your industry. A necessary expense is one that is helpful and appropriate for your trade or business. An expense does not have to be indispensable to be considered necessary.

Depends ... if you report the total GROSS sales ( including the sales taxes collected)  then payment of those taxes you collected and paid  to the proper authorities would be an expense.   If you did NOT set up  your bookkeeping on the gross income method then you would ONLY report the net sales (less of sales taxes) then you cannot deduct the sales taxes ... it is one way or the other as long as you are consistent in your method.