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	$62.78	3.325%	$64.8674	$64.87	$64.85	$64.90
Purchase #2	$237.43	4.107%	$247.1813	$247.18	$247.20	$247.20
Purchase #3	$236.73	6.572%	$252.2879	$252.29	$252.30	$252.30
Purchase #4	$183.48	5.514%	$193.5971	$193.60	$193.60	$193.60
Purchase #5	$100.72	10.720%	$111.5172	$111.52	$111.50	$111.50
Purchase #6	$34.74	7.196%	$37.2399	$37.24	$37.25	$37.20
Purchase #7	$55.84	6.374%	$59.3992	$59.40	$59.40	$59.40
7 purchase totals =	$911.72		$966.0900	$966.10	$966.10	$966.10