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	$11.43	4.369%	$11.9294	$11.93	$11.95	$11.90
Purchase #2	$123.28	12.334%	$138.4854	$138.49	$138.50	$138.50
Purchase #3	$34.57	11.759%	$38.6351	$38.64	$38.65	$38.60
Purchase #4	$111.98	13.382%	$126.9652	$126.97	$126.95	$127.00
Purchase #5	$134.46	8.471%	$145.8501	$145.85	$145.85	$145.90
Purchase #6	$215.72	8.301%	$233.6269	$233.63	$233.65	$233.60
Purchase #7	$98.87	11.195%	$109.9385	$109.94	$109.95	$109.90
7 purchase totals =	$730.31		$805.4306	$805.45	$805.50	$805.40