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	$56.35	10.602%	$62.3242	$62.32	$62.30	$62.30
Purchase #2	$65.30	10.517%	$72.1676	$72.17	$72.15	$72.20
Purchase #3	$158.47	4.663%	$165.8595	$165.86	$165.85	$165.90
Purchase #4	$60.80	4.602%	$63.598	$63.60	$63.60	$63.60
Purchase #5	$142.27	9.176%	$155.3247	$155.32	$155.30	$155.30
Purchase #6	$176.32	9.230%	$192.5943	$192.59	$192.60	$192.60
Purchase #7	$26.41	4.726%	$27.6581	$27.66	$27.65	$27.70
7 purchase totals =	$685.92		$739.5264	$739.52	$739.45	$739.60