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	$151.29	10.730%	$167.5234	$167.52	$167.50	$167.50
Purchase #2	$214.89	8.202%	$232.5153	$232.52	$232.50	$232.50
Purchase #3	$66.79	8.109%	$72.206	$72.21	$72.20	$72.20
Purchase #4	$24.45	7.854%	$26.3703	$26.37	$26.35	$26.40
Purchase #5	$126.72	4.309%	$132.1804	$132.18	$132.20	$132.20
Purchase #6	$87.72	3.324%	$90.6358	$90.64	$90.65	$90.60
Purchase #7	$103.35	10.756%	$114.4663	$114.47	$114.45	$114.50
7 purchase totals =	$775.21		$835.8975	$835.91	$835.85	$835.90