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	$132.58	8.616%	$144.0031	$144.00	$144.00	$144.00
Purchase #2	$105.56	7.137%	$113.0938	$113.09	$113.10	$113.10
Purchase #3	$228.74	11.848%	$255.8411	$255.84	$255.85	$255.80
Purchase #4	$102.39	4.372%	$106.8665	$106.87	$106.85	$106.90
Purchase #5	$139.47	7.638%	$150.1227	$150.12	$150.10	$150.10
Purchase #6	$161.91	8.870%	$176.2714	$176.27	$176.25	$176.30
Purchase #7	$61.72	13.239%	$69.8911	$69.89	$69.90	$69.90
7 purchase totals =	$932.37		$1,016.0897	$1,016.08	$1,016.05	$1,016.10