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	$130.32	10.273%	$143.7078	$143.71	$143.70	$143.70
Purchase #2	$169.68	12.273%	$190.5048	$190.50	$190.50	$190.50
Purchase #3	$70.31	4.535%	$73.4986	$73.50	$73.50	$73.50
Purchase #4	$107.31	3.631%	$111.2064	$111.21	$111.20	$111.20
Purchase #5	$151.63	3.547%	$157.0083	$157.01	$157.00	$157.00
Purchase #6	$178.47	12.370%	$200.5467	$200.55	$200.55	$200.50
Purchase #7	$61.35	6.151%	$65.1236	$65.12	$65.10	$65.10
7 purchase totals =	$869.07		$941.5962	$941.60	$941.55	$941.50