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	$112.80	13.437%	$127.9569	$127.96	$127.95	$128.00
Purchase #2	$122.63	6.392%	$130.4685	$130.47	$130.45	$130.50
Purchase #3	$208.89	9.852%	$229.4698	$229.47	$229.45	$229.50
Purchase #4	$247.77	5.788%	$262.1109	$262.11	$262.10	$262.10
Purchase #5	$10.52	12.530%	$11.8382	$11.84	$11.85	$11.80
Purchase #6	$184.84	11.770%	$206.5957	$206.60	$206.60	$206.60
Purchase #7	$66.71	6.638%	$71.1382	$71.14	$71.15	$71.10
7 purchase totals =	$954.16		$1,039.5782	$1,039.59	$1,039.55	$1,039.60