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	$204.71	5.598%	$216.1697	$216.17	$216.15	$216.20
Purchase #2	$113.47	11.379%	$126.3818	$126.38	$126.40	$126.40
Purchase #3	$145.81	13.517%	$165.5191	$165.52	$165.50	$165.50
Purchase #4	$152.34	11.182%	$169.3747	$169.37	$169.35	$169.40
Purchase #5	$90.60	4.519%	$94.6942	$94.69	$94.70	$94.70
Purchase #6	$59.94	7.783%	$64.6051	$64.61	$64.60	$64.60
Purchase #7	$241.99	12.853%	$273.093	$273.09	$273.10	$273.10
7 purchase totals =	$1,008.86		$1,109.8376	$1,109.83	$1,109.80	$1,109.90