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	$100.76	4.733%	$105.529	$105.53	$105.55	$105.50
Purchase #2	$51.68	8.861%	$56.2594	$56.26	$56.25	$56.30
Purchase #3	$176.83	7.563%	$190.2037	$190.20	$190.20	$190.20
Purchase #4	$189.93	5.491%	$200.3591	$200.36	$200.35	$200.40
Purchase #5	$145.91	3.589%	$151.1467	$151.15	$151.15	$151.10
Purchase #6	$91.87	7.577%	$98.831	$98.83	$98.85	$98.80
Purchase #7	$76.37	9.525%	$83.6442	$83.64	$83.65	$83.60
7 purchase totals =	$833.35		$885.9731	$885.97	$886.00	$885.90