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	$246.89	5.192%	$259.7085	$259.71	$259.70	$259.70
Purchase #2	$164.82	12.401%	$185.2593	$185.26	$185.25	$185.30
Purchase #3	$95.86	13.358%	$108.665	$108.67	$108.65	$108.70
Purchase #4	$72.32	4.359%	$75.4724	$75.47	$75.45	$75.50
Purchase #5	$87.42	8.189%	$94.5788	$94.58	$94.60	$94.60
Purchase #6	$211.66	5.517%	$223.3373	$223.34	$223.35	$223.30
Purchase #7	$183.53	13.757%	$208.7782	$208.78	$208.80	$208.80
7 purchase totals =	$1,062.50		$1,155.7995	$1,155.81	$1,155.80	$1,155.90