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	$138.58	11.544%	$154.5777	$154.58	$154.60	$154.60
Purchase #2	$90.52	8.314%	$98.0458	$98.05	$98.05	$98.00
Purchase #3	$163.25	13.633%	$185.5059	$185.51	$185.50	$185.50
Purchase #4	$118.64	4.448%	$123.9171	$123.92	$123.90	$123.90
Purchase #5	$202.83	5.482%	$213.9491	$213.95	$213.95	$213.90
Purchase #6	$56.72	10.474%	$62.6609	$62.66	$62.65	$62.70
Purchase #7	$61.35	3.303%	$63.3764	$63.38	$63.40	$63.40
7 purchase totals =	$831.89		$902.0329	$902.05	$902.05	$902.00