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	$171.87	3.857%	$178.499	$178.50	$178.50	$178.50
Purchase #2	$190.96	7.636%	$205.5417	$205.54	$205.55	$205.50
Purchase #3	$111.46	10.336%	$122.9805	$122.98	$123.00	$123.00
Purchase #4	$157.42	5.307%	$165.7743	$165.77	$165.75	$165.80
Purchase #5	$18.51	7.299%	$19.861	$19.86	$19.85	$19.90
Purchase #6	$27.99	12.128%	$31.3846	$31.38	$31.40	$31.40
Purchase #7	$38.55	12.576%	$43.398	$43.40	$43.40	$43.40
7 purchase totals =	$716.76		$767.4391	$767.43	$767.45	$767.50