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	$129.66	7.497%	$139.3806	$139.38	$139.40	$139.40
Purchase #2	$244.95	4.612%	$256.2471	$256.25	$256.25	$256.20
Purchase #3	$106.69	4.273%	$111.2489	$111.25	$111.25	$111.20
Purchase #4	$240.98	6.554%	$256.7738	$256.77	$256.75	$256.80
Purchase #5	$37.77	4.788%	$39.5784	$39.58	$39.60	$39.60
Purchase #6	$184.69	13.365%	$209.3738	$209.37	$209.35	$209.40
Purchase #7	$185.38	4.761%	$194.2059	$194.21	$194.20	$194.20
7 purchase totals =	$1,130.12		$1,206.8085	$1,206.81	$1,206.80	$1,206.80