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	$61.57	8.426%	$66.7579	$66.76	$66.75	$66.80
Purchase #2	$76.62	9.562%	$83.9464	$83.95	$83.95	$83.90
Purchase #3	$142.68	6.442%	$151.8714	$151.87	$151.85	$151.90
Purchase #4	$104.86	3.433%	$108.4598	$108.46	$108.45	$108.50
Purchase #5	$133.95	12.453%	$150.6308	$150.63	$150.65	$150.60
Purchase #6	$99.59	6.131%	$105.6959	$105.70	$105.70	$105.70
Purchase #7	$156.62	7.321%	$168.0862	$168.09	$168.10	$168.10
7 purchase totals =	$775.89		$835.4484	$835.46	$835.45	$835.50