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	$43.27	6.158%	$45.9346	$45.93	$45.95	$45.90
Purchase #2	$92.85	8.509%	$100.7506	$100.75	$100.75	$100.80
Purchase #3	$77.66	12.646%	$87.4809	$87.48	$87.50	$87.50
Purchase #4	$85.89	13.428%	$97.4233	$97.42	$97.40	$97.40
Purchase #5	$112.59	5.554%	$118.8432	$118.84	$118.85	$118.80
Purchase #6	$236.70	8.791%	$257.5083	$257.51	$257.50	$257.50
Purchase #7	$139.37	13.699%	$158.4623	$158.46	$158.45	$158.50
7 purchase totals =	$788.33		$866.4032	$866.39	$866.40	$866.40