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	$91.35	13.513%	$103.6941	$103.69	$103.70	$103.70
Purchase #2	$18.87	10.491%	$20.8497	$20.85	$20.85	$20.80
Purchase #3	$94.65	10.451%	$104.5419	$104.54	$104.55	$104.50
Purchase #4	$233.99	5.821%	$247.6106	$247.61	$247.60	$247.60
Purchase #5	$12.65	6.523%	$13.4752	$13.48	$13.50	$13.50
Purchase #6	$66.56	6.337%	$70.7779	$70.78	$70.80	$70.80
Purchase #7	$129.89	7.436%	$139.5486	$139.55	$139.55	$139.50
7 purchase totals =	$647.96		$700.4980	$700.50	$700.55	$700.40