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	$234.59	7.340%	$251.8089	$251.81	$251.80	$251.80
Purchase #2	$75.52	8.783%	$82.1529	$82.15	$82.15	$82.20
Purchase #3	$210.94	10.587%	$233.2722	$233.27	$233.25	$233.30
Purchase #4	$155.70	8.203%	$168.4721	$168.47	$168.45	$168.50
Purchase #5	$112.87	3.218%	$116.5022	$116.50	$116.50	$116.50
Purchase #6	$121.34	4.198%	$126.4339	$126.43	$126.45	$126.40
Purchase #7	$47.87	12.438%	$53.8241	$53.82	$53.80	$53.80
7 purchase totals =	$958.83		$1,032.4663	$1,032.45	$1,032.40	$1,032.50