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	$219.38	13.560%	$249.1279	$249.13	$249.15	$249.10
Purchase #2	$39.57	3.246%	$40.8544	$40.85	$40.85	$40.90
Purchase #3	$133.47	13.858%	$151.9663	$151.97	$151.95	$152.00
Purchase #4	$146.62	8.122%	$158.5285	$158.53	$158.55	$158.50
Purchase #5	$66.44	5.493%	$70.0895	$70.09	$70.10	$70.10
Purchase #6	$140.35	13.308%	$159.0278	$159.03	$159.05	$159.00
Purchase #7	$167.78	13.278%	$190.0578	$190.06	$190.05	$190.10
7 purchase totals =	$913.61		$1,019.6522	$1,019.66	$1,019.70	$1,019.70