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	$172.69	10.528%	$190.8708	$190.87	$190.85	$190.90
Purchase #2	$170.66	4.672%	$178.6332	$178.63	$178.65	$178.60
Purchase #3	$238.92	8.828%	$260.0119	$260.01	$260.00	$260.00
Purchase #4	$62.27	7.318%	$66.8269	$66.83	$66.85	$66.80
Purchase #5	$125.94	13.264%	$142.6447	$142.64	$142.65	$142.60
Purchase #6	$101.89	12.711%	$114.8412	$114.84	$114.85	$114.80
Purchase #7	$133.64	12.814%	$150.7646	$150.76	$150.75	$150.80
7 purchase totals =	$1,006.01		$1,104.5933	$1,104.58	$1,104.60	$1,104.50