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	$56.95	3.739%	$59.0794	$59.08	$59.10	$59.10
Purchase #2	$246.59	13.646%	$280.2397	$280.24	$280.25	$280.20
Purchase #3	$214.66	4.367%	$224.0342	$224.03	$224.05	$224.00
Purchase #4	$35.48	12.402%	$39.8802	$39.88	$39.90	$39.90
Purchase #5	$53.59	8.134%	$57.949	$57.95	$57.95	$57.90
Purchase #6	$42.31	9.170%	$46.1898	$46.19	$46.20	$46.20
Purchase #7	$60.98	9.835%	$66.9774	$66.98	$67.00	$67.00
7 purchase totals =	$710.56		$774.3497	$774.35	$774.45	$774.30