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	$8.39	6.617%	$8.9452	$8.95	$8.95	$8.90
Purchase #2	$185.61	3.556%	$192.2103	$192.21	$192.20	$192.20
Purchase #3	$143.89	3.115%	$148.3722	$148.37	$148.35	$148.40
Purchase #4	$24.90	10.429%	$27.4968	$27.50	$27.50	$27.50
Purchase #5	$226.51	13.406%	$256.8759	$256.88	$256.90	$256.90
Purchase #6	$164.89	9.169%	$180.0088	$180.01	$180.00	$180.00
Purchase #7	$240.41	7.154%	$257.6089	$257.61	$257.60	$257.60
7 purchase totals =	$994.60		$1,071.5181	$1,071.53	$1,071.50	$1,071.50