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	$76.92	6.147%	$81.6483	$81.65	$81.65	$81.60
Purchase #2	$130.32	12.377%	$146.4497	$146.45	$146.45	$146.40
Purchase #3	$210.51	5.521%	$222.1323	$222.13	$222.15	$222.10
Purchase #4	$104.86	12.190%	$117.6424	$117.64	$117.65	$117.60
Purchase #5	$125.99	13.804%	$143.3817	$143.38	$143.40	$143.40
Purchase #6	$142.50	13.516%	$161.7603	$161.76	$161.75	$161.80
Purchase #7	$104.93	6.249%	$111.4871	$111.49	$111.50	$111.50
7 purchase totals =	$896.03		$984.5018	$984.50	$984.55	$984.40