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	$199.78	7.361%	$214.4858	$214.49	$214.50	$214.50
Purchase #2	$58.56	10.259%	$64.5677	$64.57	$64.55	$64.60
Purchase #3	$51.33	10.841%	$56.8947	$56.89	$56.90	$56.90
Purchase #4	$39.66	4.409%	$41.4086	$41.41	$41.40	$41.40
Purchase #5	$138.43	5.124%	$145.5232	$145.52	$145.50	$145.50
Purchase #6	$87.59	9.491%	$95.9032	$95.90	$95.90	$95.90
Purchase #7	$10.32	9.202%	$11.2696	$11.27	$11.25	$11.30
7 purchase totals =	$585.67		$630.0528	$630.05	$630.00	$630.10