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	$176.57	8.538%	$191.6455	$191.65	$191.65	$191.60
Purchase #2	$116.78	10.741%	$129.3233	$129.32	$129.30	$129.30
Purchase #3	$172.88	3.267%	$178.528	$178.53	$178.55	$178.50
Purchase #4	$100.48	7.636%	$108.1527	$108.15	$108.15	$108.20
Purchase #5	$83.67	7.509%	$89.9528	$89.95	$89.95	$90.00
Purchase #6	$30.64	4.846%	$32.1248	$32.12	$32.10	$32.10
Purchase #7	$120.89	10.142%	$133.1507	$133.15	$133.15	$133.20
7 purchase totals =	$801.91		$862.8778	$862.87	$862.85	$862.90