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	$111.46	4.624%	$116.6139	$116.61	$116.60	$116.60
Purchase #2	$177.42	7.371%	$190.4976	$190.50	$190.50	$190.50
Purchase #3	$153.47	6.194%	$162.9759	$162.98	$163.00	$163.00
Purchase #4	$38.32	10.206%	$42.2309	$42.23	$42.25	$42.20
Purchase #5	$82.81	8.818%	$90.1122	$90.11	$90.10	$90.10
Purchase #6	$217.26	10.869%	$240.874	$240.87	$240.85	$240.90
Purchase #7	$178.98	3.394%	$185.0546	$185.05	$185.05	$185.10
7 purchase totals =	$959.72		$1,028.3591	$1,028.35	$1,028.35	$1,028.40