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	$87.42	7.578%	$94.0447	$94.04	$94.05	$94.00
Purchase #2	$125.92	12.777%	$142.0088	$142.01	$142.00	$142.00
Purchase #3	$127.47	11.844%	$142.5675	$142.57	$142.55	$142.60
Purchase #4	$124.59	6.456%	$132.6335	$132.63	$132.65	$132.60
Purchase #5	$127.45	10.547%	$140.8922	$140.89	$140.90	$140.90
Purchase #6	$102.33	3.119%	$105.5217	$105.52	$105.50	$105.50
Purchase #7	$25.27	10.202%	$27.848	$27.85	$27.85	$27.80
7 purchase totals =	$720.45		$785.5164	$785.51	$785.50	$785.40