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	$246.49	11.777%	$275.5191	$275.52	$275.50	$275.50
Purchase #2	$177.87	9.447%	$194.6734	$194.67	$194.65	$194.70
Purchase #3	$59.94	10.855%	$66.4465	$66.45	$66.45	$66.40
Purchase #4	$146.71	5.374%	$154.5942	$154.59	$154.60	$154.60
Purchase #5	$111.36	4.663%	$116.5527	$116.55	$116.55	$116.60
Purchase #6	$199.55	11.559%	$222.616	$222.62	$222.60	$222.60
Purchase #7	$38.48	6.840%	$41.112	$41.11	$41.10	$41.10
7 purchase totals =	$980.40		$1,071.5139	$1,071.51	$1,071.45	$1,071.50