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	$244.64	4.734%	$256.2213	$256.22	$256.20	$256.20
Purchase #2	$229.78	4.249%	$239.5434	$239.54	$239.55	$239.50
Purchase #3	$21.35	11.195%	$23.7401	$23.74	$23.75	$23.70
Purchase #4	$103.59	5.117%	$108.8907	$108.89	$108.90	$108.90
Purchase #5	$112.48	3.869%	$116.8319	$116.83	$116.85	$116.80
Purchase #6	$141.47	12.352%	$158.9444	$158.94	$158.95	$158.90
Purchase #7	$227.25	12.606%	$255.8971	$255.90	$255.90	$255.90
7 purchase totals =	$1,080.56		$1,160.0689	$1,160.06	$1,160.10	$1,159.90