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	$20.59	6.491%	$21.9265	$21.93	$21.95	$21.90
Purchase #2	$161.72	7.189%	$173.3461	$173.35	$173.35	$173.30
Purchase #3	$104.72	6.717%	$111.754	$111.75	$111.75	$111.80
Purchase #4	$212.95	10.142%	$234.5474	$234.55	$234.55	$234.50
Purchase #5	$239.71	4.180%	$249.7299	$249.73	$249.75	$249.70
Purchase #6	$204.64	8.741%	$222.5276	$222.53	$222.55	$222.50
Purchase #7	$30.29	6.130%	$32.1468	$32.15	$32.15	$32.10
7 purchase totals =	$974.62		$1,045.9783	$1,045.99	$1,046.05	$1,045.80