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	$58.64	11.509%	$65.3889	$65.39	$65.40	$65.40
Purchase #2	$71.70	9.407%	$78.4448	$78.44	$78.45	$78.40
Purchase #3	$107.26	10.484%	$118.5051	$118.51	$118.50	$118.50
Purchase #4	$31.57	10.729%	$34.9571	$34.96	$34.95	$35.00
Purchase #5	$144.26	12.566%	$162.3877	$162.39	$162.40	$162.40
Purchase #6	$100.69	6.851%	$107.5883	$107.59	$107.60	$107.60
Purchase #7	$122.95	4.213%	$128.1299	$128.13	$128.15	$128.10
7 purchase totals =	$637.07		$695.4018	$695.41	$695.45	$695.40