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	$75.92	4.646%	$79.4472	$79.45	$79.45	$79.40
Purchase #2	$48.80	12.396%	$54.8492	$54.85	$54.85	$54.80
Purchase #3	$42.50	8.166%	$45.9706	$45.97	$45.95	$46.00
Purchase #4	$51.87	4.275%	$54.0874	$54.09	$54.10	$54.10
Purchase #5	$34.41	5.847%	$36.422	$36.42	$36.40	$36.40
Purchase #6	$95.79	4.258%	$99.8687	$99.87	$99.85	$99.90
Purchase #7	$211.34	4.857%	$221.6048	$221.60	$221.60	$221.60
7 purchase totals =	$560.63		$592.2499	$592.25	$592.20	$592.20