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	$26.36	4.405%	$27.5212	$27.52	$27.50	$27.50
Purchase #2	$119.50	11.562%	$133.3166	$133.32	$133.30	$133.30
Purchase #3	$23.45	5.327%	$24.6992	$24.70	$24.70	$24.70
Purchase #4	$242.85	5.671%	$256.622	$256.62	$256.60	$256.60
Purchase #5	$229.53	11.429%	$255.763	$255.76	$255.75	$255.80
Purchase #6	$152.72	6.389%	$162.4773	$162.48	$162.50	$162.50
Purchase #7	$158.48	7.825%	$170.8811	$170.88	$170.90	$170.90
7 purchase totals =	$952.89		$1,031.2804	$1,031.28	$1,031.25	$1,031.30