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	$57.41	4.578%	$60.0382	$60.04	$60.05	$60.00
Purchase #2	$174.75	12.329%	$196.2949	$196.29	$196.30	$196.30
Purchase #3	$59.81	5.547%	$63.1277	$63.13	$63.15	$63.10
Purchase #4	$102.45	8.722%	$111.3857	$111.39	$111.40	$111.40
Purchase #5	$219.25	6.863%	$234.2971	$234.30	$234.30	$234.30
Purchase #6	$193.86	9.628%	$212.5248	$212.52	$212.50	$212.50
Purchase #7	$233.67	13.664%	$265.5987	$265.60	$265.60	$265.60
7 purchase totals =	$1,041.20		$1,143.2671	$1,143.27	$1,143.30	$1,143.20