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	$64.59	3.630%	$66.9346	$66.93	$66.95	$66.90
Purchase #2	$216.30	12.333%	$242.9763	$242.98	$243.00	$243.00
Purchase #3	$45.69	9.682%	$50.1137	$50.11	$50.10	$50.10
Purchase #4	$250.67	11.496%	$279.487	$279.49	$279.50	$279.50
Purchase #5	$44.46	13.256%	$50.3536	$50.35	$50.35	$50.40
Purchase #6	$214.43	6.305%	$227.9498	$227.95	$227.95	$227.90
Purchase #7	$83.59	4.776%	$87.5823	$87.58	$87.60	$87.60
7 purchase totals =	$919.73		$1,005.3973	$1,005.39	$1,005.45	$1,005.40