Are the sales taxes part of a retailer's sales?

No, sales taxes (VAT) are not part of retailer`s sales. 

Sales taxes go to credit account directly to paid to taxes authority 

Collected amount of sales taxes not included in company sales

For example when you sell goods with taxes10% 

Debit

Accounts receivable by all amount.100000

Credit 

Sales.                                                    90000

Taxes on sales.                                    10000

yes it is