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	$210.96	7.522%	$226.8284	$226.83	$226.85	$226.80
Purchase #2	$111.82	11.421%	$124.591	$124.59	$124.60	$124.60
Purchase #3	$136.70	4.211%	$142.4564	$142.46	$142.45	$142.50
Purchase #4	$157.50	6.791%	$168.1958	$168.20	$168.20	$168.20
Purchase #5	$76.28	3.246%	$78.756	$78.76	$78.75	$78.80
Purchase #6	$31.43	8.473%	$34.0931	$34.09	$34.10	$34.10
Purchase #7	$205.60	5.296%	$216.4886	$216.49	$216.50	$216.50
7 purchase totals =	$930.29		$991.4093	$991.42	$991.45	$991.50