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	$188.85	6.160%	$200.4832	$200.48	$200.50	$200.50
Purchase #2	$125.71	9.698%	$137.9014	$137.90	$137.90	$137.90
Purchase #3	$174.65	6.403%	$185.8328	$185.83	$185.85	$185.80
Purchase #4	$152.45	13.828%	$173.5308	$173.53	$173.55	$173.50
Purchase #5	$34.34	3.363%	$35.4949	$35.49	$35.50	$35.50
Purchase #6	$167.52	9.422%	$183.3037	$183.30	$183.30	$183.30
Purchase #7	$11.88	6.700%	$12.676	$12.68	$12.70	$12.70
7 purchase totals =	$855.40		$929.2228	$929.21	$929.30	$929.20