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	$54.97	11.689%	$61.3954	$61.40	$61.40	$61.40
Purchase #2	$215.69	12.116%	$241.823	$241.82	$241.80	$241.80
Purchase #3	$189.78	7.509%	$204.0306	$204.03	$204.05	$204.00
Purchase #4	$96.83	3.730%	$100.4418	$100.44	$100.45	$100.40
Purchase #5	$95.90	4.817%	$100.5195	$100.52	$100.50	$100.50
Purchase #6	$126.69	9.703%	$138.9827	$138.98	$139.00	$139.00
Purchase #7	$194.94	13.134%	$220.5434	$220.54	$220.55	$220.50
7 purchase totals =	$974.80		$1,067.7364	$1,067.73	$1,067.75	$1,067.60