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	$138.67	6.624%	$147.8555	$147.86	$147.85	$147.90
Purchase #2	$88.40	13.748%	$100.5532	$100.55	$100.55	$100.60
Purchase #3	$81.70	8.656%	$88.772	$88.77	$88.75	$88.80
Purchase #4	$154.49	3.536%	$159.9528	$159.95	$159.95	$160.00
Purchase #5	$140.89	12.637%	$158.6943	$158.69	$158.70	$158.70
Purchase #6	$117.69	10.843%	$130.4511	$130.45	$130.45	$130.50
Purchase #7	$223.92	3.429%	$231.5982	$231.60	$231.60	$231.60
7 purchase totals =	$945.76		$1,017.8771	$1,017.87	$1,017.85	$1,018.10