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	$208.77	4.286%	$217.7179	$217.72	$217.70	$217.70
Purchase #2	$103.54	12.422%	$116.4017	$116.40	$116.40	$116.40
Purchase #3	$161.78	12.423%	$181.8779	$181.88	$181.90	$181.90
Purchase #4	$187.96	13.666%	$213.6466	$213.65	$213.65	$213.60
Purchase #5	$214.89	8.669%	$233.5188	$233.52	$233.50	$233.50
Purchase #6	$198.42	6.285%	$210.8907	$210.89	$210.90	$210.90
Purchase #7	$170.45	6.443%	$181.4321	$181.43	$181.45	$181.40
7 purchase totals =	$1,245.81		$1,355.4857	$1,355.49	$1,355.50	$1,355.40