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	$131.29	6.638%	$140.005	$140.01	$140.00	$140.00
Purchase #2	$72.97	11.702%	$81.5089	$81.51	$81.50	$81.50
Purchase #3	$179.67	12.278%	$201.7299	$201.73	$201.75	$201.70
Purchase #4	$131.25	10.157%	$144.5811	$144.58	$144.60	$144.60
Purchase #5	$226.77	12.834%	$255.8737	$255.87	$255.85	$255.90
Purchase #6	$101.52	10.846%	$112.5309	$112.53	$112.55	$112.50
Purchase #7	$107.69	4.351%	$112.3756	$112.38	$112.40	$112.40
7 purchase totals =	$951.16		$1,048.6051	$1,048.61	$1,048.65	$1,048.60