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	$29.83	8.768%	$32.4455	$32.45	$32.45	$32.40
Purchase #2	$234.27	13.153%	$265.0835	$265.08	$265.10	$265.10
Purchase #3	$30.60	5.587%	$32.3096	$32.31	$32.30	$32.30
Purchase #4	$225.72	13.784%	$256.8332	$256.83	$256.85	$256.80
Purchase #5	$192.67	13.738%	$219.139	$219.14	$219.15	$219.10
Purchase #6	$27.58	5.468%	$29.0881	$29.09	$29.10	$29.10
Purchase #7	$231.81	8.456%	$251.4119	$251.41	$251.40	$251.40
7 purchase totals =	$972.48		$1,086.3108	$1,086.31	$1,086.35	$1,086.20