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	$183.61	9.308%	$200.7004	$200.70	$200.70	$200.70
Purchase #2	$210.46	6.382%	$223.8916	$223.89	$223.90	$223.90
Purchase #3	$128.65	13.162%	$145.5829	$145.58	$145.60	$145.60
Purchase #4	$28.84	13.580%	$32.7565	$32.76	$32.75	$32.80
Purchase #5	$26.85	9.397%	$29.3731	$29.37	$29.35	$29.40
Purchase #6	$66.88	8.369%	$72.4772	$72.48	$72.50	$72.50
Purchase #7	$224.78	5.301%	$236.6956	$236.70	$236.70	$236.70
7 purchase totals =	$870.07		$941.4773	$941.48	$941.50	$941.60