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	$76.89	11.184%	$85.4894	$85.49	$85.50	$85.50
Purchase #2	$151.85	3.747%	$157.5398	$157.54	$157.55	$157.50
Purchase #3	$44.38	8.494%	$48.1496	$48.15	$48.15	$48.10
Purchase #4	$180.89	8.776%	$196.7649	$196.76	$196.75	$196.80
Purchase #5	$240.27	7.102%	$257.334	$257.33	$257.35	$257.30
Purchase #6	$116.59	3.403%	$120.5576	$120.56	$120.55	$120.60
Purchase #7	$241.81	7.136%	$259.0656	$259.07	$259.05	$259.10
7 purchase totals =	$1,052.68		$1,124.9009	$1,124.90	$1,124.90	$1,124.90