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	$99.45	4.381%	$103.8069	$103.81	$103.80	$103.80
Purchase #2	$176.50	11.384%	$196.5928	$196.59	$196.60	$196.60
Purchase #3	$229.93	11.310%	$255.9351	$255.94	$255.95	$255.90
Purchase #4	$205.78	9.687%	$225.7139	$225.71	$225.70	$225.70
Purchase #5	$52.43	13.297%	$59.4016	$59.40	$59.40	$59.40
Purchase #6	$82.94	4.293%	$86.5006	$86.50	$86.50	$86.50
Purchase #7	$222.34	8.451%	$241.13	$241.13	$241.15	$241.10
7 purchase totals =	$1,069.37		$1,169.0809	$1,169.08	$1,169.10	$1,169.00