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	$186.33	12.524%	$209.666	$209.67	$209.65	$209.70
Purchase #2	$85.31	10.693%	$94.4322	$94.43	$94.45	$94.40
Purchase #3	$247.37	10.823%	$274.1429	$274.14	$274.15	$274.10
Purchase #4	$63.30	11.554%	$70.6137	$70.61	$70.60	$70.60
Purchase #5	$241.86	8.523%	$262.4737	$262.47	$262.45	$262.50
Purchase #6	$166.77	3.481%	$172.5753	$172.58	$172.60	$172.60
Purchase #7	$187.98	13.383%	$213.1374	$213.14	$213.15	$213.10
7 purchase totals =	$1,178.92		$1,297.0412	$1,297.04	$1,297.05	$1,297.00