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	$221.87	11.403%	$247.1698	$247.17	$247.15	$247.20
Purchase #2	$169.48	13.195%	$191.8429	$191.84	$191.85	$191.80
Purchase #3	$233.58	3.485%	$241.7203	$241.72	$241.70	$241.70
Purchase #4	$88.76	3.474%	$91.8435	$91.84	$91.85	$91.80
Purchase #5	$178.76	9.853%	$196.3732	$196.37	$196.35	$196.40
Purchase #6	$149.59	6.474%	$159.2745	$159.27	$159.25	$159.30
Purchase #7	$19.92	3.243%	$20.566	$20.57	$20.55	$20.60
7 purchase totals =	$1,061.96		$1,148.7902	$1,148.78	$1,148.70	$1,148.80