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	$67.34	13.382%	$76.3514	$76.35	$76.35	$76.40
Purchase #2	$43.25	4.186%	$45.0604	$45.06	$45.05	$45.10
Purchase #3	$37.42	5.841%	$39.6057	$39.61	$39.60	$39.60
Purchase #4	$58.34	12.709%	$65.7544	$65.75	$65.75	$65.80
Purchase #5	$50.37	13.351%	$57.0949	$57.09	$57.10	$57.10
Purchase #6	$127.89	3.832%	$132.7907	$132.79	$132.80	$132.80
Purchase #7	$238.78	12.745%	$269.2125	$269.21	$269.20	$269.20
7 purchase totals =	$623.39		$685.8700	$685.86	$685.85	$686.00