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	$180.46	8.821%	$196.3784	$196.38	$196.40	$196.40
Purchase #2	$116.45	13.456%	$132.1195	$132.12	$132.10	$132.10
Purchase #3	$241.35	4.834%	$253.0169	$253.02	$253.00	$253.00
Purchase #4	$151.28	5.853%	$160.1344	$160.13	$160.15	$160.10
Purchase #5	$97.84	7.215%	$104.8992	$104.90	$104.90	$104.90
Purchase #6	$141.50	9.186%	$154.4982	$154.50	$154.50	$154.50
Purchase #7	$224.53	12.606%	$252.8343	$252.83	$252.85	$252.80
7 purchase totals =	$1,153.41		$1,253.8809	$1,253.88	$1,253.90	$1,253.80