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	$54.74	8.162%	$59.2079	$59.21	$59.20	$59.20
Purchase #2	$45.61	9.182%	$49.7979	$49.80	$49.80	$49.80
Purchase #3	$45.97	3.509%	$47.5831	$47.58	$47.60	$47.60
Purchase #4	$87.67	13.424%	$99.4388	$99.44	$99.45	$99.40
Purchase #5	$143.44	11.820%	$160.3946	$160.39	$160.40	$160.40
Purchase #6	$59.78	9.344%	$65.3658	$65.37	$65.35	$65.40
Purchase #7	$213.38	10.722%	$236.2586	$236.26	$236.25	$236.30
7 purchase totals =	$650.59		$718.0467	$718.05	$718.05	$718.10