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	$212.38	13.730%	$241.5398	$241.54	$241.55	$241.50
Purchase #2	$79.25	10.405%	$87.496	$87.50	$87.50	$87.50
Purchase #3	$168.35	7.491%	$180.9611	$180.96	$180.95	$181.00
Purchase #4	$48.78	8.388%	$52.8717	$52.87	$52.85	$52.90
Purchase #5	$177.50	8.136%	$191.9414	$191.94	$191.95	$191.90
Purchase #6	$218.72	12.288%	$245.5963	$245.60	$245.60	$245.60
Purchase #7	$47.47	13.618%	$53.9345	$53.93	$53.95	$53.90
7 purchase totals =	$952.45		$1,054.3408	$1,054.34	$1,054.35	$1,054.30