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	$216.25	10.179%	$238.2621	$238.26	$238.25	$238.30
Purchase #2	$163.55	6.252%	$173.7751	$173.78	$173.80	$173.80
Purchase #3	$169.33	9.390%	$185.2301	$185.23	$185.25	$185.20
Purchase #4	$175.98	13.304%	$199.3924	$199.39	$199.40	$199.40
Purchase #5	$158.75	8.450%	$172.1644	$172.16	$172.15	$172.20
Purchase #6	$222.94	7.139%	$238.8557	$238.86	$238.85	$238.90
Purchase #7	$132.87	11.856%	$148.6231	$148.62	$148.60	$148.60
7 purchase totals =	$1,239.67		$1,356.3029	$1,356.30	$1,356.30	$1,356.40