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	$193.39	11.705%	$216.0263	$216.03	$216.05	$216.00
Purchase #2	$62.73	8.298%	$67.9353	$67.94	$67.95	$67.90
Purchase #3	$71.44	12.545%	$80.4021	$80.40	$80.40	$80.40
Purchase #4	$119.57	11.125%	$132.8722	$132.87	$132.85	$132.90
Purchase #5	$94.88	13.686%	$107.8653	$107.87	$107.85	$107.90
Purchase #6	$100.89	7.182%	$108.1359	$108.14	$108.15	$108.10
Purchase #7	$67.93	6.491%	$72.3393	$72.34	$72.35	$72.30
7 purchase totals =	$710.83		$785.5764	$785.59	$785.60	$785.50