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	$54.76	11.370%	$60.9862	$60.99	$61.00	$61.00
Purchase #2	$155.34	11.244%	$172.8064	$172.81	$172.80	$172.80
Purchase #3	$49.46	6.281%	$52.5666	$52.57	$52.55	$52.60
Purchase #4	$38.92	5.732%	$41.1509	$41.15	$41.15	$41.20
Purchase #5	$204.98	9.154%	$223.7439	$223.74	$223.75	$223.70
Purchase #6	$106.61	10.284%	$117.5738	$117.57	$117.55	$117.60
Purchase #7	$53.87	9.622%	$59.0534	$59.05	$59.05	$59.10
7 purchase totals =	$663.94		$727.8812	$727.88	$727.85	$728.00