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	$65.54	4.471%	$68.4703	$68.47	$68.45	$68.50
Purchase #2	$138.48	6.362%	$147.2901	$147.29	$147.30	$147.30
Purchase #3	$118.87	4.157%	$123.8114	$123.81	$123.80	$123.80
Purchase #4	$60.74	3.199%	$62.6831	$62.68	$62.70	$62.70
Purchase #5	$105.82	10.161%	$116.5724	$116.57	$116.55	$116.60
Purchase #6	$11.63	11.238%	$12.937	$12.94	$12.95	$12.90
Purchase #7	$52.66	13.187%	$59.6043	$59.60	$59.60	$59.60
7 purchase totals =	$553.74		$591.3686	$591.36	$591.35	$591.40