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	$95.93	13.426%	$108.8096	$108.81	$108.80	$108.80
Purchase #2	$106.27	9.216%	$116.0638	$116.06	$116.05	$116.10
Purchase #3	$44.78	13.802%	$50.9605	$50.96	$50.95	$51.00
Purchase #4	$14.53	13.867%	$16.5449	$16.54	$16.55	$16.50
Purchase #5	$111.59	6.663%	$119.0252	$119.03	$119.05	$119.00
Purchase #6	$211.43	5.444%	$222.9402	$222.94	$222.95	$222.90
Purchase #7	$132.88	4.802%	$139.2609	$139.26	$139.25	$139.30
7 purchase totals =	$717.41		$773.6051	$773.60	$773.60	$773.60