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	$223.97	10.327%	$247.0994	$247.10	$247.10	$247.10
Purchase #2	$87.84	13.679%	$99.8556	$99.86	$99.85	$99.90
Purchase #3	$60.28	10.845%	$66.8174	$66.82	$66.80	$66.80
Purchase #4	$37.94	4.357%	$39.593	$39.59	$39.60	$39.60
Purchase #5	$52.91	6.863%	$56.5412	$56.54	$56.55	$56.50
Purchase #6	$59.89	13.641%	$68.0596	$68.06	$68.05	$68.10
Purchase #7	$129.50	13.363%	$146.8051	$146.81	$146.80	$146.80
7 purchase totals =	$652.33		$724.7713	$724.78	$724.75	$724.80