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	$245.49	10.841%	$272.1036	$272.10	$272.10	$272.10
Purchase #2	$71.53	10.102%	$78.756	$78.76	$78.75	$78.80
Purchase #3	$158.47	8.693%	$172.2458	$172.25	$172.25	$172.20
Purchase #4	$39.89	8.476%	$43.2711	$43.27	$43.25	$43.30
Purchase #5	$111.95	12.548%	$125.9975	$126.00	$126.00	$126.00
Purchase #6	$97.52	9.401%	$106.6879	$106.69	$106.70	$106.70
Purchase #7	$206.98	3.585%	$214.4002	$214.40	$214.40	$214.40
7 purchase totals =	$931.83		$1,013.4621	$1,013.47	$1,013.45	$1,013.50