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	$174.78	5.859%	$185.0204	$185.02	$185.00	$185.00
Purchase #2	$19.71	11.326%	$21.9424	$21.94	$21.95	$21.90
Purchase #3	$149.86	9.692%	$164.3844	$164.38	$164.40	$164.40
Purchase #4	$88.99	5.390%	$93.7866	$93.79	$93.80	$93.80
Purchase #5	$8.47	12.416%	$9.5216	$9.52	$9.50	$9.50
Purchase #6	$18.25	11.308%	$20.3137	$20.31	$20.30	$20.30
Purchase #7	$10.25	13.222%	$11.6053	$11.61	$11.60	$11.60
7 purchase totals =	$470.31		$506.5744	$506.57	$506.55	$506.50