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	$61.58	6.390%	$65.515	$65.52	$65.50	$65.50
Purchase #2	$122.55	3.490%	$126.827	$126.83	$126.85	$126.80
Purchase #3	$160.51	7.609%	$172.7232	$172.72	$172.70	$172.70
Purchase #4	$47.79	10.709%	$52.9078	$52.91	$52.90	$52.90
Purchase #5	$61.79	6.121%	$65.5722	$65.57	$65.55	$65.60
Purchase #6	$161.32	3.858%	$167.5437	$167.54	$167.55	$167.50
Purchase #7	$126.85	11.227%	$141.0914	$141.09	$141.10	$141.10
7 purchase totals =	$742.39		$792.1803	$792.18	$792.15	$792.10