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	$65.93	7.795%	$71.0692	$71.07	$71.05	$71.10
Purchase #2	$243.46	9.188%	$265.8291	$265.83	$265.85	$265.80
Purchase #3	$174.73	11.194%	$194.2893	$194.29	$194.30	$194.30
Purchase #4	$246.81	13.271%	$279.5642	$279.56	$279.55	$279.60
Purchase #5	$58.52	6.227%	$62.164	$62.16	$62.15	$62.20
Purchase #6	$158.80	13.113%	$179.6234	$179.62	$179.60	$179.60
Purchase #7	$60.72	7.817%	$65.4665	$65.47	$65.45	$65.50
7 purchase totals =	$1,008.97		$1,118.0057	$1,118.00	$1,117.95	$1,118.10