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	$237.28	9.504%	$259.8311	$259.83	$259.85	$259.80
Purchase #2	$21.58	13.443%	$24.481	$24.48	$24.50	$24.50
Purchase #3	$61.76	9.348%	$67.5333	$67.53	$67.55	$67.50
Purchase #4	$24.54	4.421%	$25.6249	$25.62	$25.60	$25.60
Purchase #5	$152.78	10.356%	$168.6019	$168.60	$168.60	$168.60
Purchase #6	$143.89	9.492%	$157.548	$157.55	$157.55	$157.50
Purchase #7	$59.32	4.600%	$62.0487	$62.05	$62.05	$62.00
7 purchase totals =	$701.15		$765.6689	$765.66	$765.70	$765.50