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	$233.46	13.731%	$265.5164	$265.52	$265.50	$265.50
Purchase #2	$89.50	9.870%	$98.3337	$98.33	$98.35	$98.30
Purchase #3	$191.42	13.403%	$217.076	$217.08	$217.10	$217.10
Purchase #4	$221.63	11.509%	$247.1374	$247.14	$247.15	$247.10
Purchase #5	$18.60	5.549%	$19.6321	$19.63	$19.65	$19.60
Purchase #6	$178.90	11.525%	$199.5182	$199.52	$199.50	$199.50
Purchase #7	$80.26	11.853%	$89.7732	$89.77	$89.75	$89.80
7 purchase totals =	$1,013.77		$1,136.9870	$1,136.99	$1,137.00	$1,136.90