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	$202.61	3.480%	$209.6608	$209.66	$209.65	$209.70
Purchase #2	$61.85	8.483%	$67.0967	$67.10	$67.10	$67.10
Purchase #3	$34.80	11.509%	$38.8051	$38.81	$38.80	$38.80
Purchase #4	$63.79	6.231%	$67.7648	$67.76	$67.75	$67.80
Purchase #5	$124.46	7.564%	$133.8742	$133.87	$133.85	$133.90
Purchase #6	$129.25	11.103%	$143.6006	$143.60	$143.60	$143.60
Purchase #7	$64.94	4.285%	$67.7227	$67.72	$67.70	$67.70
7 purchase totals =	$681.70		$728.5249	$728.52	$728.45	$728.60