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	$219.91	6.775%	$234.8089	$234.81	$234.80	$234.80
Purchase #2	$48.66	8.610%	$52.8496	$52.85	$52.85	$52.80
Purchase #3	$194.27	8.448%	$210.6819	$210.68	$210.70	$210.70
Purchase #4	$78.80	13.168%	$89.1764	$89.18	$89.20	$89.20
Purchase #5	$172.47	11.409%	$192.1471	$192.15	$192.15	$192.10
Purchase #6	$222.53	8.869%	$242.2662	$242.27	$242.25	$242.30
Purchase #7	$205.59	8.791%	$223.6634	$223.66	$223.65	$223.70
7 purchase totals =	$1,142.23		$1,245.5935	$1,245.60	$1,245.60	$1,245.60