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	$206.86	10.375%	$228.3217	$228.32	$228.30	$228.30
Purchase #2	$152.43	3.643%	$157.983	$157.98	$158.00	$158.00
Purchase #3	$75.35	10.713%	$83.4222	$83.42	$83.40	$83.40
Purchase #4	$126.46	12.750%	$142.5837	$142.58	$142.60	$142.60
Purchase #5	$43.35	12.283%	$48.6747	$48.67	$48.65	$48.70
Purchase #6	$151.71	6.577%	$161.688	$161.69	$161.70	$161.70
Purchase #7	$98.79	13.189%	$111.8194	$111.82	$111.80	$111.80
7 purchase totals =	$854.95		$934.4927	$934.48	$934.45	$934.50