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	$70.35	3.318%	$72.6842	$72.68	$72.70	$72.70
Purchase #2	$90.40	10.667%	$100.043	$100.04	$100.05	$100.00
Purchase #3	$55.85	9.516%	$61.1647	$61.16	$61.15	$61.20
Purchase #4	$136.52	10.508%	$150.8655	$150.87	$150.85	$150.90
Purchase #5	$81.39	13.761%	$92.5901	$92.59	$92.60	$92.60
Purchase #6	$60.28	5.870%	$63.8184	$63.82	$63.80	$63.80
Purchase #7	$83.56	4.159%	$87.0353	$87.04	$87.05	$87.00
7 purchase totals =	$578.35		$628.2012	$628.20	$628.20	$628.20