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	$56.94	13.117%	$64.4088	$64.41	$64.40	$64.40
Purchase #2	$192.81	8.193%	$208.6069	$208.61	$208.60	$208.60
Purchase #3	$90.69	10.158%	$99.9023	$99.90	$99.90	$99.90
Purchase #4	$150.71	4.558%	$157.5794	$157.58	$157.60	$157.60
Purchase #5	$246.82	11.808%	$275.9645	$275.96	$275.95	$276.00
Purchase #6	$141.66	4.207%	$147.6196	$147.62	$147.60	$147.60
Purchase #7	$143.39	5.632%	$151.4657	$151.47	$151.45	$151.50
7 purchase totals =	$1,023.02		$1,105.5472	$1,105.55	$1,105.50	$1,105.60