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	$112.78	7.162%	$120.8573	$120.86	$120.85	$120.90
Purchase #2	$85.26	9.237%	$93.1355	$93.14	$93.15	$93.10
Purchase #3	$48.27	12.630%	$54.3665	$54.37	$54.35	$54.40
Purchase #4	$44.76	4.342%	$46.7035	$46.70	$46.70	$46.70
Purchase #5	$20.48	5.295%	$21.5644	$21.56	$21.55	$21.60
Purchase #6	$113.28	4.703%	$118.6076	$118.61	$118.60	$118.60
Purchase #7	$214.98	10.822%	$238.2451	$238.25	$238.25	$238.20
7 purchase totals =	$639.81		$693.4799	$693.49	$693.45	$693.50