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	$167.51	9.210%	$182.9377	$182.94	$182.95	$182.90
Purchase #2	$227.61	13.115%	$257.4611	$257.46	$257.45	$257.50
Purchase #3	$153.50	10.705%	$169.9322	$169.93	$169.95	$169.90
Purchase #4	$34.38	7.652%	$37.0108	$37.01	$37.00	$37.00
Purchase #5	$48.97	5.352%	$51.5909	$51.59	$51.60	$51.60
Purchase #6	$105.68	5.855%	$111.8676	$111.87	$111.85	$111.90
Purchase #7	$10.49	3.670%	$10.875	$10.88	$10.90	$10.90
7 purchase totals =	$748.14		$821.6753	$821.68	$821.70	$821.70