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	$186.69	7.218%	$200.1653	$200.17	$200.15	$200.20
Purchase #2	$104.61	6.698%	$111.6168	$111.62	$111.60	$111.60
Purchase #3	$120.87	9.379%	$132.2064	$132.21	$132.20	$132.20
Purchase #4	$30.42	7.246%	$32.6242	$32.62	$32.60	$32.60
Purchase #5	$81.27	7.500%	$87.3653	$87.37	$87.35	$87.40
Purchase #6	$207.79	4.238%	$216.5961	$216.60	$216.60	$216.60
Purchase #7	$126.38	10.322%	$139.4249	$139.42	$139.40	$139.40
7 purchase totals =	$858.03		$919.9990	$920.01	$919.90	$920.00