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	$103.58	10.536%	$114.4932	$114.49	$114.50	$114.50
Purchase #2	$212.88	5.302%	$224.1669	$224.17	$224.15	$224.20
Purchase #3	$139.77	11.237%	$155.476	$155.48	$155.50	$155.50
Purchase #4	$205.70	12.766%	$231.9597	$231.96	$231.95	$232.00
Purchase #5	$26.78	3.841%	$27.8086	$27.81	$27.80	$27.80
Purchase #6	$148.50	11.213%	$165.1513	$165.15	$165.15	$165.20
Purchase #7	$79.75	12.619%	$89.8137	$89.81	$89.80	$89.80
7 purchase totals =	$916.96		$1,008.8694	$1,008.87	$1,008.85	$1,009.00