The monthly payment uses the standard amortizing formula. The amount is the number you enter. The rate is divided by 12. The term is the number of months on the form. Total interest is the payment times the number of months, minus the amount borrowed.
A $30,000 loan at 7% for 60 months has a fixed monthly principal-and-interest payment. Sales tax is not added on top. If the amount you typed already includes tax and fees, those costs are inside the payment. If it does not, they are missing.
Tax, title, and dealer fees are not added unless they are already in the amount. A down payment should be subtracted before you type the amount, or entered in the down-payment field when the form has one.