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	$178.48	6.819%	$190.6506	$190.65	$190.65	$190.70
Purchase #2	$65.95	10.269%	$72.7224	$72.72	$72.70	$72.70
Purchase #3	$143.85	5.698%	$152.0466	$152.05	$152.05	$152.00
Purchase #4	$225.29	13.496%	$255.6951	$255.70	$255.70	$255.70
Purchase #5	$156.97	9.232%	$171.4615	$171.46	$171.45	$171.50
Purchase #6	$169.37	11.259%	$188.4394	$188.44	$188.45	$188.40
Purchase #7	$138.87	5.735%	$146.8342	$146.83	$146.85	$146.80
7 purchase totals =	$1,078.78		$1,177.8498	$1,177.85	$1,177.85	$1,177.80