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	$131.40	11.120%	$146.0117	$146.01	$146.00	$146.00
Purchase #2	$145.89	8.462%	$158.2352	$158.24	$158.25	$158.20
Purchase #3	$49.31	7.367%	$52.9427	$52.94	$52.95	$52.90
Purchase #4	$32.72	6.331%	$34.7915	$34.79	$34.80	$34.80
Purchase #5	$199.93	7.680%	$215.2846	$215.28	$215.30	$215.30
Purchase #6	$28.51	11.795%	$31.8728	$31.87	$31.85	$31.90
Purchase #7	$177.85	8.116%	$192.2843	$192.28	$192.30	$192.30
7 purchase totals =	$765.61		$831.4228	$831.41	$831.45	$831.40