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	$62.98	4.593%	$65.8727	$65.87	$65.85	$65.90
Purchase #2	$61.70	6.138%	$65.4871	$65.49	$65.50	$65.50
Purchase #3	$161.59	8.580%	$175.4544	$175.45	$175.45	$175.50
Purchase #4	$73.78	5.689%	$77.9773	$77.98	$78.00	$78.00
Purchase #5	$67.55	6.373%	$71.855	$71.86	$71.85	$71.90
Purchase #6	$226.36	13.164%	$256.158	$256.16	$256.15	$256.20
Purchase #7	$145.34	4.422%	$151.7669	$151.77	$151.75	$151.80
7 purchase totals =	$799.30		$864.5714	$864.58	$864.55	$864.80