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	$9.40	12.542%	$10.5789	$10.58	$10.60	$10.60
Purchase #2	$79.49	13.448%	$90.1798	$90.18	$90.20	$90.20
Purchase #3	$244.59	5.568%	$258.2088	$258.21	$258.20	$258.20
Purchase #4	$19.40	5.658%	$20.4977	$20.50	$20.50	$20.50
Purchase #5	$162.25	4.734%	$169.9309	$169.93	$169.95	$169.90
Purchase #6	$158.43	6.634%	$168.9402	$168.94	$168.95	$168.90
Purchase #7	$130.81	8.560%	$142.0073	$142.01	$142.00	$142.00
7 purchase totals =	$804.37		$860.3436	$860.35	$860.40	$860.30