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	$37.52	11.350%	$41.7785	$41.78	$41.80	$41.80
Purchase #2	$87.61	10.731%	$97.0114	$97.01	$97.00	$97.00
Purchase #3	$10.75	3.434%	$11.1192	$11.12	$11.10	$11.10
Purchase #4	$52.64	12.218%	$59.0716	$59.07	$59.05	$59.10
Purchase #5	$166.54	7.739%	$179.4285	$179.43	$179.45	$179.40
Purchase #6	$21.86	6.271%	$23.2308	$23.23	$23.25	$23.20
Purchase #7	$34.83	7.692%	$37.5091	$37.51	$37.50	$37.50
7 purchase totals =	$411.75		$449.1491	$449.15	$449.15	$449.10