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	$83.66	13.356%	$94.8336	$94.83	$94.85	$94.80
Purchase #2	$95.40	8.580%	$103.5853	$103.59	$103.60	$103.60
Purchase #3	$158.67	6.150%	$168.4282	$168.43	$168.45	$168.40
Purchase #4	$140.25	12.705%	$158.0688	$158.07	$158.05	$158.10
Purchase #5	$111.47	12.446%	$125.3436	$125.34	$125.35	$125.30
Purchase #6	$57.45	4.606%	$60.0961	$60.10	$60.10	$60.10
Purchase #7	$177.87	12.816%	$200.6658	$200.67	$200.65	$200.70
7 purchase totals =	$824.77		$911.0214	$911.03	$911.05	$911.00