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	$126.73	7.868%	$136.7011	$136.70	$136.70	$136.70
Purchase #2	$60.55	4.807%	$63.4606	$63.46	$63.45	$63.50
Purchase #3	$60.55	10.585%	$66.9592	$66.96	$66.95	$67.00
Purchase #4	$212.50	12.842%	$239.7893	$239.79	$239.80	$239.80
Purchase #5	$200.82	11.403%	$223.7195	$223.72	$223.70	$223.70
Purchase #6	$156.31	7.161%	$167.5034	$167.50	$167.50	$167.50
Purchase #7	$244.61	4.462%	$255.5245	$255.52	$255.50	$255.50
7 purchase totals =	$1,062.07		$1,153.6576	$1,153.65	$1,153.60	$1,153.70