Every seller of food with respect to which a tax is levied under this article shall collect the amount of tax imposed under this article from the purchases on whom the same is levied at the time payment for such food become due and payable, whether payment is to be made in cash or on credit by means of a credit card or otherwise. The amount of tax owed by the purchaser shall be added to the cost of the food by the seller who shall pay the taxes collected to the county as provided in this article. Taxes collected by the seller shall be held in trust by the seller until remitted to the county.