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	$118.98	3.871%	$123.5857	$123.59	$123.60	$123.60
Purchase #2	$133.54	8.126%	$144.3915	$144.39	$144.40	$144.40
Purchase #3	$196.75	4.633%	$205.8654	$205.87	$205.85	$205.90
Purchase #4	$122.33	7.518%	$131.5268	$131.53	$131.55	$131.50
Purchase #5	$117.66	4.520%	$122.9782	$122.98	$123.00	$123.00
Purchase #6	$249.64	6.154%	$265.0028	$265.00	$265.00	$265.00
Purchase #7	$193.59	9.725%	$212.4166	$212.42	$212.40	$212.40
7 purchase totals =	$1,132.49		$1,205.7670	$1,205.78	$1,205.80	$1,205.80