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	$119.98	9.578%	$131.4717	$131.47	$131.45	$131.50
Purchase #2	$146.97	7.162%	$157.496	$157.50	$157.50	$157.50
Purchase #3	$140.30	8.680%	$152.478	$152.48	$152.50	$152.50
Purchase #4	$60.66	7.614%	$65.2787	$65.28	$65.30	$65.30
Purchase #5	$161.50	6.692%	$172.3076	$172.31	$172.30	$172.30
Purchase #6	$226.66	13.798%	$257.9345	$257.93	$257.95	$257.90
Purchase #7	$68.94	11.104%	$76.5951	$76.60	$76.60	$76.60
7 purchase totals =	$925.01		$1,013.5616	$1,013.57	$1,013.60	$1,013.60