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	$21.92	7.717%	$23.6116	$23.61	$23.60	$23.60
Purchase #2	$84.67	5.710%	$89.5047	$89.50	$89.50	$89.50
Purchase #3	$136.32	10.470%	$150.5927	$150.59	$150.60	$150.60
Purchase #4	$163.57	3.127%	$168.6848	$168.68	$168.70	$168.70
Purchase #5	$178.33	12.547%	$200.7051	$200.71	$200.70	$200.70
Purchase #6	$222.79	7.600%	$239.722	$239.72	$239.70	$239.70
Purchase #7	$125.30	10.509%	$138.4678	$138.47	$138.45	$138.50
7 purchase totals =	$932.90		$1,011.2887	$1,011.28	$1,011.25	$1,011.30