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	$24.54	8.427%	$26.608	$26.61	$26.60	$26.60
Purchase #2	$114.34	11.195%	$127.1404	$127.14	$127.15	$127.10
Purchase #3	$223.39	12.639%	$251.6243	$251.62	$251.60	$251.60
Purchase #4	$77.45	7.285%	$83.0922	$83.09	$83.10	$83.10
Purchase #5	$151.66	8.675%	$164.8165	$164.82	$164.80	$164.80
Purchase #6	$204.77	11.582%	$228.4865	$228.49	$228.50	$228.50
Purchase #7	$190.37	12.833%	$214.8002	$214.80	$214.80	$214.80
7 purchase totals =	$986.52		$1,096.5681	$1,096.57	$1,096.55	$1,096.50