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	$105.50	8.536%	$114.5055	$114.51	$114.50	$114.50
Purchase #2	$129.27	11.766%	$144.4799	$144.48	$144.50	$144.50
Purchase #3	$250.29	12.472%	$281.5062	$281.51	$281.50	$281.50
Purchase #4	$56.34	4.597%	$58.9299	$58.93	$58.95	$58.90
Purchase #5	$152.48	10.761%	$168.8884	$168.89	$168.90	$168.90
Purchase #6	$190.53	3.770%	$197.713	$197.71	$197.70	$197.70
Purchase #7	$216.37	13.455%	$245.4826	$245.48	$245.50	$245.50
7 purchase totals =	$1,100.78		$1,211.5055	$1,211.51	$1,211.55	$1,211.50