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	$63.72	8.720%	$69.2764	$69.28	$69.30	$69.30
Purchase #2	$24.86	10.500%	$27.4703	$27.47	$27.45	$27.50
Purchase #3	$76.66	8.869%	$83.459	$83.46	$83.45	$83.50
Purchase #4	$14.75	5.580%	$15.5731	$15.57	$15.55	$15.60
Purchase #5	$57.29	11.536%	$63.899	$63.90	$63.90	$63.90
Purchase #6	$153.26	3.823%	$159.1191	$159.12	$159.10	$159.10
Purchase #7	$240.98	3.267%	$248.8528	$248.85	$248.85	$248.90
7 purchase totals =	$631.52		$667.6497	$667.65	$667.60	$667.80