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	$162.80	4.742%	$170.52	$170.52	$170.50	$170.50
Purchase #2	$55.74	3.325%	$57.5934	$57.59	$57.60	$57.60
Purchase #3	$48.55	5.840%	$51.3853	$51.39	$51.40	$51.40
Purchase #4	$189.93	13.133%	$214.8735	$214.87	$214.85	$214.90
Purchase #5	$78.88	8.408%	$85.5122	$85.51	$85.50	$85.50
Purchase #6	$54.44	9.594%	$59.663	$59.66	$59.65	$59.70
Purchase #7	$81.90	13.370%	$92.85	$92.85	$92.85	$92.90
7 purchase totals =	$672.24		$732.3974	$732.39	$732.35	$732.50