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	$76.96	7.748%	$82.9229	$82.92	$82.90	$82.90
Purchase #2	$117.86	12.455%	$132.5395	$132.54	$132.55	$132.50
Purchase #3	$43.93	13.570%	$49.8913	$49.89	$49.90	$49.90
Purchase #4	$163.25	5.486%	$172.2059	$172.21	$172.20	$172.20
Purchase #5	$95.52	13.627%	$108.5365	$108.54	$108.55	$108.50
Purchase #6	$200.88	8.294%	$217.541	$217.54	$217.55	$217.50
Purchase #7	$112.79	6.421%	$120.0322	$120.03	$120.05	$120.00
7 purchase totals =	$811.19		$883.6693	$883.67	$883.70	$883.50