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	$200.46	9.520%	$219.5438	$219.54	$219.55	$219.50
Purchase #2	$214.59	3.466%	$222.0277	$222.03	$222.05	$222.00
Purchase #3	$198.71	13.473%	$225.4822	$225.48	$225.50	$225.50
Purchase #4	$141.52	3.720%	$146.7845	$146.78	$146.80	$146.80
Purchase #5	$106.72	5.748%	$112.8543	$112.85	$112.85	$112.90
Purchase #6	$115.34	12.792%	$130.0943	$130.09	$130.10	$130.10
Purchase #7	$38.88	8.736%	$42.2766	$42.28	$42.30	$42.30
7 purchase totals =	$1,016.22		$1,099.0634	$1,099.05	$1,099.15	$1,099.10