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	$140.29	9.314%	$153.3566	$153.36	$153.35	$153.40
Purchase #2	$25.78	5.309%	$27.1487	$27.15	$27.15	$27.10
Purchase #3	$45.90	6.458%	$48.8642	$48.86	$48.85	$48.90
Purchase #4	$157.37	4.667%	$164.7145	$164.71	$164.70	$164.70
Purchase #5	$59.37	8.579%	$64.4634	$64.46	$64.45	$64.50
Purchase #6	$75.28	9.152%	$82.1696	$82.17	$82.15	$82.20
Purchase #7	$119.79	11.252%	$133.2688	$133.27	$133.25	$133.30
7 purchase totals =	$623.78		$673.9858	$673.98	$673.90	$674.10