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	$130.57	8.873%	$142.1555	$142.16	$142.15	$142.20
Purchase #2	$11.97	4.142%	$12.4658	$12.47	$12.45	$12.50
Purchase #3	$21.29	4.146%	$22.1727	$22.17	$22.15	$22.20
Purchase #4	$65.57	10.530%	$72.4745	$72.47	$72.45	$72.50
Purchase #5	$242.32	7.403%	$260.2589	$260.26	$260.25	$260.30
Purchase #6	$206.42	7.242%	$221.3689	$221.37	$221.35	$221.40
Purchase #7	$90.50	11.546%	$100.9491	$100.95	$100.95	$100.90
7 purchase totals =	$768.64		$831.8454	$831.85	$831.75	$832.00