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	$52.78	13.352%	$59.8272	$59.83	$59.85	$59.80
Purchase #2	$214.31	8.768%	$233.1007	$233.10	$233.10	$233.10
Purchase #3	$112.70	5.523%	$118.9244	$118.92	$118.90	$118.90
Purchase #4	$205.61	4.325%	$214.5026	$214.50	$214.50	$214.50
Purchase #5	$245.48	10.769%	$271.9157	$271.92	$271.90	$271.90
Purchase #6	$151.95	3.864%	$157.8213	$157.82	$157.80	$157.80
Purchase #7	$51.83	13.286%	$58.7161	$58.72	$58.70	$58.70
7 purchase totals =	$1,034.66		$1,114.8080	$1,114.81	$1,114.75	$1,114.70