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	$54.46	12.629%	$61.3378	$61.34	$61.35	$61.30
Purchase #2	$247.77	3.542%	$256.546	$256.55	$256.55	$256.50
Purchase #3	$120.76	6.364%	$128.4452	$128.45	$128.45	$128.40
Purchase #4	$48.31	7.434%	$51.9014	$51.90	$51.90	$51.90
Purchase #5	$103.51	5.112%	$108.8014	$108.80	$108.80	$108.80
Purchase #6	$185.85	10.666%	$205.6728	$205.67	$205.65	$205.70
Purchase #7	$148.31	4.208%	$154.5509	$154.55	$154.55	$154.60
7 purchase totals =	$908.97		$967.2555	$967.26	$967.25	$967.20