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	$105.41	11.405%	$117.432	$117.43	$117.45	$117.40
Purchase #2	$241.60	7.462%	$259.6282	$259.63	$259.65	$259.60
Purchase #3	$60.38	9.136%	$65.8963	$65.90	$65.90	$65.90
Purchase #4	$150.82	4.334%	$157.3565	$157.36	$157.35	$157.40
Purchase #5	$237.89	7.246%	$255.1275	$255.13	$255.15	$255.10
Purchase #6	$171.47	9.547%	$187.8402	$187.84	$187.85	$187.80
Purchase #7	$183.32	8.143%	$198.2477	$198.25	$198.25	$198.20
7 purchase totals =	$1,150.89		$1,241.5284	$1,241.54	$1,241.60	$1,241.40