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	$65.27	10.449%	$72.0901	$72.09	$72.10	$72.10
Purchase #2	$35.92	8.293%	$38.8988	$38.90	$38.90	$38.90
Purchase #3	$8.79	6.366%	$9.3496	$9.35	$9.35	$9.30
Purchase #4	$182.78	6.462%	$194.5912	$194.59	$194.60	$194.60
Purchase #5	$217.67	3.282%	$224.8139	$224.81	$224.80	$224.80
Purchase #6	$92.47	8.211%	$100.0627	$100.06	$100.05	$100.10
Purchase #7	$42.63	5.716%	$45.0667	$45.07	$45.05	$45.10
7 purchase totals =	$645.53		$684.8730	$684.87	$684.85	$684.90