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	$61.32	8.800%	$66.7162	$66.72	$66.70	$66.70
Purchase #2	$241.68	12.697%	$272.3661	$272.37	$272.35	$272.40
Purchase #3	$132.25	12.117%	$148.2747	$148.27	$148.25	$148.30
Purchase #4	$148.40	11.581%	$165.5862	$165.59	$165.60	$165.60
Purchase #5	$199.64	11.635%	$222.8681	$222.87	$222.85	$222.90
Purchase #6	$244.78	7.685%	$263.5913	$263.59	$263.60	$263.60
Purchase #7	$196.98	11.410%	$219.4554	$219.46	$219.45	$219.50
7 purchase totals =	$1,225.05		$1,358.8580	$1,358.87	$1,358.80	$1,359.00