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	$179.89	13.556%	$204.2759	$204.28	$204.30	$204.30
Purchase #2	$240.89	10.205%	$265.4728	$265.47	$265.45	$265.50
Purchase #3	$40.86	7.781%	$44.0393	$44.04	$44.05	$44.00
Purchase #4	$235.57	8.509%	$255.6147	$255.61	$255.60	$255.60
Purchase #5	$20.95	13.792%	$23.8394	$23.84	$23.85	$23.80
Purchase #6	$145.25	9.867%	$159.5818	$159.58	$159.60	$159.60
Purchase #7	$139.41	8.734%	$151.5861	$151.59	$151.60	$151.60
7 purchase totals =	$1,002.82		$1,104.4100	$1,104.41	$1,104.45	$1,104.40