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	$242.85	10.776%	$269.0195	$269.02	$269.00	$269.00
Purchase #2	$157.55	9.491%	$172.5031	$172.50	$172.50	$172.50
Purchase #3	$132.53	7.855%	$142.9402	$142.94	$142.95	$142.90
Purchase #4	$57.89	9.677%	$63.492	$63.49	$63.50	$63.50
Purchase #5	$10.69	9.784%	$11.7359	$11.74	$11.75	$11.70
Purchase #6	$98.67	13.656%	$112.1444	$112.14	$112.15	$112.10
Purchase #7	$59.27	12.201%	$66.5015	$66.50	$66.50	$66.50
7 purchase totals =	$759.45		$838.3366	$838.33	$838.35	$838.20