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	$215.36	7.284%	$231.0468	$231.05	$231.05	$231.00
Purchase #2	$31.95	6.576%	$34.051	$34.05	$34.05	$34.10
Purchase #3	$77.75	10.245%	$85.7155	$85.72	$85.70	$85.70
Purchase #4	$103.92	4.429%	$108.5226	$108.52	$108.50	$108.50
Purchase #5	$237.77	8.541%	$258.0779	$258.08	$258.10	$258.10
Purchase #6	$229.67	11.172%	$255.3287	$255.33	$255.35	$255.30
Purchase #7	$117.94	12.652%	$132.8618	$132.86	$132.85	$132.90
7 purchase totals =	$1,014.36		$1,105.6043	$1,105.61	$1,105.60	$1,105.60