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	$67.30	7.872%	$72.5979	$72.60	$72.60	$72.60
Purchase #2	$89.60	12.405%	$100.7149	$100.71	$100.70	$100.70
Purchase #3	$182.47	4.762%	$191.1592	$191.16	$191.15	$191.20
Purchase #4	$123.72	11.693%	$138.1866	$138.19	$138.20	$138.20
Purchase #5	$199.33	4.756%	$208.8101	$208.81	$208.80	$208.80
Purchase #6	$35.77	5.656%	$37.7932	$37.79	$37.80	$37.80
Purchase #7	$221.25	11.177%	$245.9791	$245.98	$246.00	$246.00
7 purchase totals =	$919.44		$995.2410	$995.24	$995.25	$995.30