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	$71.34	8.634%	$77.4995	$77.50	$77.50	$77.50
Purchase #2	$16.33	8.389%	$17.6999	$17.70	$17.70	$17.70
Purchase #3	$104.82	6.730%	$111.8744	$111.87	$111.85	$111.90
Purchase #4	$173.96	3.814%	$180.5948	$180.59	$180.60	$180.60
Purchase #5	$125.42	11.171%	$139.4307	$139.43	$139.45	$139.40
Purchase #6	$170.68	6.189%	$181.2434	$181.24	$181.25	$181.20
Purchase #7	$153.98	3.832%	$159.8805	$159.88	$159.90	$159.90
7 purchase totals =	$816.53		$868.2232	$868.21	$868.25	$868.20