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	$66.71	10.763%	$73.89	$73.89	$73.90	$73.90
Purchase #2	$11.78	4.169%	$12.2711	$12.27	$12.25	$12.30
Purchase #3	$100.37	5.553%	$105.9435	$105.94	$105.95	$105.90
Purchase #4	$64.73	11.106%	$71.9189	$71.92	$71.90	$71.90
Purchase #5	$64.57	7.619%	$69.4896	$69.49	$69.50	$69.50
Purchase #6	$231.70	8.491%	$251.3736	$251.37	$251.35	$251.40
Purchase #7	$114.84	12.218%	$128.8712	$128.87	$128.85	$128.90
7 purchase totals =	$654.70		$713.7579	$713.75	$713.70	$713.80