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	$136.41	11.143%	$151.6102	$151.61	$151.60	$151.60
Purchase #2	$37.34	4.651%	$39.0767	$39.08	$39.10	$39.10
Purchase #3	$75.90	7.326%	$81.4604	$81.46	$81.45	$81.50
Purchase #4	$45.85	10.613%	$50.7161	$50.72	$50.70	$50.70
Purchase #5	$65.85	5.309%	$69.346	$69.35	$69.35	$69.30
Purchase #6	$36.87	4.323%	$38.4639	$38.46	$38.45	$38.50
Purchase #7	$129.42	6.545%	$137.8905	$137.89	$137.90	$137.90
7 purchase totals =	$527.64		$568.5638	$568.57	$568.55	$568.60