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	$92.89	13.700%	$105.6159	$105.62	$105.60	$105.60
Purchase #2	$101.27	6.151%	$107.4991	$107.50	$107.50	$107.50
Purchase #3	$63.50	4.200%	$66.167	$66.17	$66.15	$66.20
Purchase #4	$229.26	8.160%	$247.9676	$247.97	$247.95	$248.00
Purchase #5	$40.63	6.257%	$43.1722	$43.17	$43.15	$43.20
Purchase #6	$10.77	10.874%	$11.9411	$11.94	$11.95	$11.90
Purchase #7	$145.61	13.414%	$165.1421	$165.14	$165.15	$165.10
7 purchase totals =	$683.93		$747.5050	$747.51	$747.45	$747.50