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	$104.93	6.613%	$111.869	$111.87	$111.85	$111.90
Purchase #2	$174.55	8.735%	$189.7969	$189.80	$189.80	$189.80
Purchase #3	$143.88	6.660%	$153.4624	$153.46	$153.45	$153.50
Purchase #4	$27.64	11.754%	$30.8888	$30.89	$30.90	$30.90
Purchase #5	$143.35	5.616%	$151.4005	$151.40	$151.40	$151.40
Purchase #6	$63.81	3.572%	$66.0893	$66.09	$66.10	$66.10
Purchase #7	$39.36	8.346%	$42.645	$42.65	$42.65	$42.60
7 purchase totals =	$697.52		$746.1519	$746.16	$746.15	$746.20