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	$60.48	7.630%	$65.0946	$65.09	$65.10	$65.10
Purchase #2	$234.60	8.762%	$255.1557	$255.16	$255.15	$255.20
Purchase #3	$80.30	11.478%	$89.5168	$89.52	$89.50	$89.50
Purchase #4	$238.49	11.302%	$265.4441	$265.44	$265.45	$265.40
Purchase #5	$226.37	13.124%	$256.0788	$256.08	$256.10	$256.10
Purchase #6	$41.56	8.677%	$45.1662	$45.17	$45.15	$45.20
Purchase #7	$173.72	5.742%	$183.695	$183.70	$183.70	$183.70
7 purchase totals =	$1,055.52		$1,160.1512	$1,160.16	$1,160.15	$1,160.20