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	$55.53	7.683%	$59.7964	$59.80	$59.80	$59.80
Purchase #2	$68.97	4.865%	$72.3254	$72.33	$72.35	$72.30
Purchase #3	$49.71	10.348%	$54.854	$54.85	$54.85	$54.90
Purchase #4	$151.82	7.420%	$163.085	$163.09	$163.10	$163.10
Purchase #5	$26.25	12.821%	$29.6155	$29.62	$29.60	$29.60
Purchase #6	$10.90	4.145%	$11.3518	$11.35	$11.35	$11.40
Purchase #7	$37.49	5.246%	$39.4567	$39.46	$39.45	$39.50
7 purchase totals =	$400.67		$430.4848	$430.50	$430.50	$430.60