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	$229.81	11.144%	$255.42	$255.42	$255.40	$255.40
Purchase #2	$38.43	6.166%	$40.7996	$40.80	$40.80	$40.80
Purchase #3	$117.97	6.691%	$125.8634	$125.86	$125.85	$125.90
Purchase #4	$132.54	8.145%	$143.3354	$143.34	$143.35	$143.30
Purchase #5	$43.65	5.472%	$46.0385	$46.04	$46.05	$46.00
Purchase #6	$123.63	11.205%	$137.4827	$137.48	$137.50	$137.50
Purchase #7	$156.33	4.158%	$162.8302	$162.83	$162.85	$162.80
7 purchase totals =	$842.36		$911.7698	$911.77	$911.80	$911.70