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	$103.72	8.458%	$112.4926	$112.49	$112.50	$112.50
Purchase #2	$104.73	11.195%	$116.4545	$116.45	$116.45	$116.50
Purchase #3	$100.52	10.639%	$111.2143	$111.21	$111.20	$111.20
Purchase #4	$211.96	13.473%	$240.5174	$240.52	$240.50	$240.50
Purchase #5	$118.47	3.472%	$122.5833	$122.58	$122.60	$122.60
Purchase #6	$193.88	13.815%	$220.6645	$220.66	$220.65	$220.70
Purchase #7	$150.48	4.389%	$157.0846	$157.08	$157.10	$157.10
7 purchase totals =	$983.76		$1,081.0112	$1,080.99	$1,081.00	$1,081.10