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	$105.33	7.302%	$113.0212	$113.02	$113.00	$113.00
Purchase #2	$235.30	8.583%	$255.4958	$255.50	$255.50	$255.50
Purchase #3	$139.94	12.750%	$157.7824	$157.78	$157.80	$157.80
Purchase #4	$94.27	6.328%	$100.2354	$100.24	$100.25	$100.20
Purchase #5	$131.51	13.214%	$148.8877	$148.89	$148.90	$148.90
Purchase #6	$130.38	12.163%	$146.2381	$146.24	$146.25	$146.20
Purchase #7	$40.72	5.181%	$42.8297	$42.83	$42.85	$42.80
7 purchase totals =	$877.45		$964.4903	$964.50	$964.55	$964.40