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	$59.49	5.263%	$62.621	$62.62	$62.60	$62.60
Purchase #2	$218.73	12.409%	$245.8722	$245.87	$245.85	$245.90
Purchase #3	$67.63	7.162%	$72.4737	$72.47	$72.45	$72.50
Purchase #4	$58.46	5.128%	$61.4578	$61.46	$61.45	$61.50
Purchase #5	$59.72	11.263%	$66.4463	$66.45	$66.45	$66.40
Purchase #6	$62.36	8.687%	$67.7772	$67.78	$67.80	$67.80
Purchase #7	$21.68	9.583%	$23.7576	$23.76	$23.75	$23.80
7 purchase totals =	$548.07		$600.4058	$600.41	$600.35	$600.50