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	$217.32	4.721%	$227.5797	$227.58	$227.60	$227.60
Purchase #2	$61.39	8.131%	$66.3816	$66.38	$66.40	$66.40
Purchase #3	$98.81	10.186%	$108.8748	$108.87	$108.85	$108.90
Purchase #4	$31.26	11.734%	$34.928	$34.93	$34.95	$34.90
Purchase #5	$174.85	5.525%	$184.5105	$184.51	$184.50	$184.50
Purchase #6	$109.58	3.197%	$113.0833	$113.08	$113.10	$113.10
Purchase #7	$103.67	5.633%	$109.5097	$109.51	$109.50	$109.50
7 purchase totals =	$796.88		$844.8676	$844.86	$844.90	$844.90