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	$140.32	3.701%	$145.5132	$145.51	$145.50	$145.50
Purchase #2	$202.90	13.293%	$229.8715	$229.87	$229.85	$229.90
Purchase #3	$53.28	11.680%	$59.5031	$59.50	$59.50	$59.50
Purchase #4	$73.69	3.143%	$76.0061	$76.01	$76.00	$76.00
Purchase #5	$60.76	5.449%	$64.0708	$64.07	$64.05	$64.10
Purchase #6	$219.95	3.422%	$227.4767	$227.48	$227.50	$227.50
Purchase #7	$231.82	6.618%	$247.1618	$247.16	$247.15	$247.20
7 purchase totals =	$982.72		$1,049.6032	$1,049.60	$1,049.55	$1,049.70