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	$172.51	4.574%	$180.4006	$180.40	$180.40	$180.40
Purchase #2	$213.94	13.451%	$242.7171	$242.72	$242.70	$242.70
Purchase #3	$223.96	6.495%	$238.5062	$238.51	$238.50	$238.50
Purchase #4	$131.78	8.802%	$143.3793	$143.38	$143.40	$143.40
Purchase #5	$126.25	11.491%	$140.7574	$140.76	$140.75	$140.80
Purchase #6	$143.65	10.550%	$158.8051	$158.81	$158.80	$158.80
Purchase #7	$248.72	5.646%	$262.7627	$262.76	$262.75	$262.80
7 purchase totals =	$1,260.81		$1,367.3284	$1,367.34	$1,367.30	$1,367.40