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	$229.93	13.468%	$260.897	$260.90	$260.90	$260.90
Purchase #2	$153.62	8.637%	$166.8882	$166.89	$166.90	$166.90
Purchase #3	$89.89	6.120%	$95.3913	$95.39	$95.40	$95.40
Purchase #4	$191.35	12.181%	$214.6583	$214.66	$214.65	$214.70
Purchase #5	$215.42	6.217%	$228.8127	$228.81	$228.80	$228.80
Purchase #6	$143.86	9.227%	$157.134	$157.13	$157.15	$157.10
Purchase #7	$37.77	7.677%	$40.6696	$40.67	$40.65	$40.70
7 purchase totals =	$1,061.84		$1,164.4511	$1,164.45	$1,164.45	$1,164.50