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	$66.79	8.868%	$72.7129	$72.71	$72.70	$72.70
Purchase #2	$10.45	6.122%	$11.0897	$11.09	$11.10	$11.10
Purchase #3	$246.47	11.431%	$274.644	$274.64	$274.65	$274.60
Purchase #4	$206.66	13.667%	$234.9042	$234.90	$234.90	$234.90
Purchase #5	$134.83	6.762%	$143.9472	$143.95	$143.95	$143.90
Purchase #6	$189.48	3.655%	$196.4055	$196.41	$196.40	$196.40
Purchase #7	$116.30	4.377%	$121.3905	$121.39	$121.40	$121.40
7 purchase totals =	$970.98		$1,055.0940	$1,055.09	$1,055.10	$1,055.00