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	$167.48	7.667%	$180.3207	$180.32	$180.30	$180.30
Purchase #2	$136.77	3.244%	$141.2068	$141.21	$141.20	$141.20
Purchase #3	$112.39	4.136%	$117.0385	$117.04	$117.05	$117.00
Purchase #4	$194.92	10.629%	$215.638	$215.64	$215.65	$215.60
Purchase #5	$140.74	3.345%	$145.4478	$145.45	$145.45	$145.40
Purchase #6	$90.91	9.464%	$99.5137	$99.51	$99.50	$99.50
Purchase #7	$117.42	12.716%	$132.3511	$132.35	$132.35	$132.40
7 purchase totals =	$960.63		$1,031.5166	$1,031.52	$1,031.50	$1,031.40