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	$22.83	5.837%	$24.1626	$24.16	$24.15	$24.20
Purchase #2	$55.94	7.671%	$60.2312	$60.23	$60.25	$60.20
Purchase #3	$157.90	4.234%	$164.5855	$164.59	$164.60	$164.60
Purchase #4	$12.98	4.845%	$13.6089	$13.61	$13.60	$13.60
Purchase #5	$9.78	10.716%	$10.828	$10.83	$10.85	$10.80
Purchase #6	$71.79	7.204%	$76.9618	$76.96	$76.95	$77.00
Purchase #7	$112.72	12.771%	$127.1155	$127.12	$127.10	$127.10
7 purchase totals =	$443.94		$477.4935	$477.50	$477.50	$477.50