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	$52.80	4.116%	$54.9732	$54.97	$54.95	$55.00
Purchase #2	$184.59	11.302%	$205.4524	$205.45	$205.45	$205.50
Purchase #3	$21.29	11.761%	$23.7939	$23.79	$23.80	$23.80
Purchase #4	$204.43	7.406%	$219.5701	$219.57	$219.55	$219.60
Purchase #5	$204.82	5.797%	$216.6934	$216.69	$216.70	$216.70
Purchase #6	$51.95	4.539%	$54.308	$54.31	$54.30	$54.30
Purchase #7	$111.54	10.762%	$123.5439	$123.54	$123.55	$123.50
7 purchase totals =	$831.42		$898.3349	$898.32	$898.30	$898.40