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	$63.56	3.601%	$65.8488	$65.85	$65.85	$65.80
Purchase #2	$143.69	10.776%	$159.174	$159.17	$159.15	$159.20
Purchase #3	$57.33	3.380%	$59.2678	$59.27	$59.25	$59.30
Purchase #4	$149.56	5.756%	$158.1687	$158.17	$158.15	$158.20
Purchase #5	$170.77	9.363%	$186.7592	$186.76	$186.75	$186.80
Purchase #6	$57.31	13.777%	$65.2056	$65.21	$65.20	$65.20
Purchase #7	$250.72	6.546%	$267.1321	$267.13	$267.15	$267.10
7 purchase totals =	$892.94		$961.5562	$961.56	$961.50	$961.60