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	$247.40	11.117%	$274.9035	$274.90	$274.90	$274.90
Purchase #2	$240.66	6.549%	$256.4208	$256.42	$256.40	$256.40
Purchase #3	$25.65	7.143%	$27.4822	$27.48	$27.50	$27.50
Purchase #4	$91.42	12.508%	$102.8548	$102.85	$102.85	$102.90
Purchase #5	$101.94	3.409%	$105.4151	$105.42	$105.40	$105.40
Purchase #6	$112.89	12.583%	$127.0949	$127.09	$127.10	$127.10
Purchase #7	$52.83	4.125%	$55.0092	$55.01	$55.00	$55.00
7 purchase totals =	$872.79		$949.1805	$949.17	$949.15	$949.20