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	$155.45	8.625%	$168.8576	$168.86	$168.85	$168.90
Purchase #2	$14.65	8.508%	$15.8964	$15.90	$15.90	$15.90
Purchase #3	$126.81	8.168%	$137.1678	$137.17	$137.15	$137.20
Purchase #4	$171.56	11.688%	$191.6119	$191.61	$191.60	$191.60
Purchase #5	$170.29	4.637%	$178.1863	$178.19	$178.20	$178.20
Purchase #6	$102.93	8.336%	$111.5102	$111.51	$111.50	$111.50
Purchase #7	$161.85	9.523%	$177.263	$177.26	$177.25	$177.30
7 purchase totals =	$903.54		$980.4932	$980.50	$980.45	$980.60