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	$86.95	6.488%	$92.5913	$92.59	$92.60	$92.60
Purchase #2	$199.69	11.206%	$222.0673	$222.07	$222.05	$222.10
Purchase #3	$51.46	6.265%	$54.684	$54.68	$54.70	$54.70
Purchase #4	$5.59	11.387%	$6.2265	$6.23	$6.25	$6.20
Purchase #5	$146.47	3.389%	$151.4339	$151.43	$151.45	$151.40
Purchase #6	$21.56	6.110%	$22.8773	$22.88	$22.90	$22.90
Purchase #7	$9.78	4.282%	$10.1988	$10.20	$10.20	$10.20
7 purchase totals =	$521.50		$560.0791	$560.08	$560.15	$560.10