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	$133.42	4.770%	$139.7841	$139.78	$139.80	$139.80
Purchase #2	$189.35	8.580%	$205.5962	$205.60	$205.60	$205.60
Purchase #3	$162.69	5.823%	$172.1634	$172.16	$172.15	$172.20
Purchase #4	$59.47	5.587%	$62.7926	$62.79	$62.80	$62.80
Purchase #5	$188.67	12.498%	$212.25	$212.25	$212.25	$212.30
Purchase #6	$103.36	5.234%	$108.7699	$108.77	$108.75	$108.80
Purchase #7	$76.31	9.606%	$83.6403	$83.64	$83.65	$83.60
7 purchase totals =	$913.27		$984.9965	$984.99	$985.00	$985.10