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	$42.95	3.616%	$44.5031	$44.50	$44.50	$44.50
Purchase #2	$61.79	6.632%	$65.8879	$65.89	$65.90	$65.90
Purchase #3	$101.89	9.576%	$111.647	$111.65	$111.65	$111.60
Purchase #4	$17.39	13.789%	$19.7879	$19.79	$19.80	$19.80
Purchase #5	$41.58	13.395%	$47.1496	$47.15	$47.15	$47.10
Purchase #6	$197.37	5.437%	$208.101	$208.10	$208.10	$208.10
Purchase #7	$58.64	4.867%	$61.494	$61.49	$61.50	$61.50
7 purchase totals =	$521.61		$558.5705	$558.57	$558.60	$558.50