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	$72.50	12.442%	$81.5205	$81.52	$81.50	$81.50
Purchase #2	$35.47	3.599%	$36.7466	$36.75	$36.75	$36.70
Purchase #3	$113.89	8.826%	$123.9419	$123.94	$123.95	$123.90
Purchase #4	$243.84	10.521%	$269.4944	$269.49	$269.50	$269.50
Purchase #5	$100.87	5.787%	$106.7073	$106.71	$106.70	$106.70
Purchase #6	$69.71	4.511%	$72.8546	$72.85	$72.85	$72.90
Purchase #7	$30.60	13.829%	$34.8317	$34.83	$34.85	$34.80
7 purchase totals =	$666.88		$726.0970	$726.09	$726.10	$726.00