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	$53.60	12.271%	$60.1773	$60.18	$60.20	$60.20
Purchase #2	$145.72	13.832%	$165.876	$165.88	$165.90	$165.90
Purchase #3	$101.55	4.375%	$105.9928	$105.99	$106.00	$106.00
Purchase #4	$43.66	5.480%	$46.0526	$46.05	$46.05	$46.10
Purchase #5	$52.38	13.442%	$59.4209	$59.42	$59.40	$59.40
Purchase #6	$159.78	11.784%	$178.6085	$178.61	$178.60	$178.60
Purchase #7	$12.41	3.551%	$12.8507	$12.85	$12.85	$12.90
7 purchase totals =	$569.10		$628.9788	$628.98	$629.00	$629.10