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	$169.52	6.683%	$180.849	$180.85	$180.85	$180.80
Purchase #2	$12.33	8.473%	$13.3747	$13.37	$13.35	$13.40
Purchase #3	$137.54	9.733%	$150.9268	$150.93	$150.95	$150.90
Purchase #4	$48.43	7.130%	$51.8831	$51.88	$51.90	$51.90
Purchase #5	$158.78	10.757%	$175.86	$175.86	$175.85	$175.90
Purchase #6	$42.53	10.139%	$46.8421	$46.84	$46.85	$46.80
Purchase #7	$189.85	3.195%	$195.9157	$195.92	$195.90	$195.90
7 purchase totals =	$758.98		$815.6514	$815.65	$815.65	$815.60