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	$167.28	6.703%	$178.4928	$178.49	$178.50	$178.50
Purchase #2	$177.70	5.739%	$187.8982	$187.90	$187.90	$187.90
Purchase #3	$11.43	4.419%	$11.9351	$11.94	$11.95	$11.90
Purchase #4	$215.43	3.325%	$222.593	$222.59	$222.60	$222.60
Purchase #5	$29.83	4.410%	$31.1455	$31.15	$31.15	$31.10
Purchase #6	$49.43	11.148%	$54.9405	$54.94	$54.95	$54.90
Purchase #7	$102.96	5.704%	$108.8328	$108.83	$108.85	$108.80
7 purchase totals =	$754.06		$795.8379	$795.84	$795.90	$795.70