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	$114.52	10.731%	$126.8091	$126.81	$126.80	$126.80
Purchase #2	$91.68	8.555%	$99.5232	$99.52	$99.50	$99.50
Purchase #3	$122.98	7.169%	$131.7964	$131.80	$131.80	$131.80
Purchase #4	$152.52	3.858%	$158.4042	$158.40	$158.40	$158.40
Purchase #5	$242.50	13.586%	$275.4461	$275.45	$275.45	$275.40
Purchase #6	$108.87	4.315%	$113.5677	$113.57	$113.55	$113.60
Purchase #7	$72.46	7.583%	$77.9546	$77.95	$77.95	$78.00
7 purchase totals =	$905.53		$983.5013	$983.50	$983.45	$983.50