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	$182.71	4.456%	$190.8516	$190.85	$190.85	$190.90
Purchase #2	$131.66	3.380%	$136.1101	$136.11	$136.10	$136.10
Purchase #3	$157.54	7.438%	$169.2578	$169.26	$169.25	$169.30
Purchase #4	$50.93	6.187%	$54.081	$54.08	$54.10	$54.10
Purchase #5	$161.98	7.311%	$173.8224	$173.82	$173.80	$173.80
Purchase #6	$19.72	10.160%	$21.7236	$21.72	$21.70	$21.70
Purchase #7	$54.85	11.457%	$61.1342	$61.13	$61.15	$61.10
7 purchase totals =	$759.39		$806.9807	$806.97	$806.95	$807.00