Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.72	11.221%	$205.4474	$205.45	$205.45	$205.40
Purchase #2	$67.64	13.225%	$76.5854	$76.59	$76.60	$76.60
Purchase #3	$216.25	13.275%	$244.9572	$244.96	$244.95	$245.00
Purchase #4	$177.87	12.552%	$200.1962	$200.20	$200.20	$200.20
Purchase #5	$177.65	11.698%	$198.4315	$198.43	$198.45	$198.40
Purchase #6	$19.83	4.466%	$20.7156	$20.72	$20.70	$20.70
Purchase #7	$125.79	13.644%	$142.9528	$142.95	$142.95	$143.00
7 purchase totals =	$969.75		$1,089.2861	$1,089.30	$1,089.30	$1,089.30