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	$127.69	10.429%	$141.0068	$141.01	$141.00	$141.00
Purchase #2	$57.83	8.686%	$62.8531	$62.85	$62.85	$62.90
Purchase #3	$239.99	6.725%	$256.1293	$256.13	$256.15	$256.10
Purchase #4	$169.71	6.128%	$180.1098	$180.11	$180.10	$180.10
Purchase #5	$42.79	7.194%	$45.8683	$45.87	$45.85	$45.90
Purchase #6	$69.66	13.124%	$78.8022	$78.80	$78.80	$78.80
Purchase #7	$237.80	12.214%	$266.8449	$266.84	$266.85	$266.80
7 purchase totals =	$945.47		$1,031.6144	$1,031.61	$1,031.60	$1,031.60