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	$145.62	7.776%	$156.9434	$156.94	$156.95	$156.90
Purchase #2	$61.39	10.527%	$67.8525	$67.85	$67.85	$67.90
Purchase #3	$145.71	3.311%	$150.5345	$150.53	$150.55	$150.50
Purchase #4	$217.60	13.652%	$247.3068	$247.31	$247.30	$247.30
Purchase #5	$132.52	6.438%	$141.0516	$141.05	$141.05	$141.10
Purchase #6	$107.78	3.338%	$111.3777	$111.38	$111.40	$111.40
Purchase #7	$163.83	3.147%	$168.9857	$168.99	$169.00	$169.00
7 purchase totals =	$974.45		$1,044.0522	$1,044.05	$1,044.10	$1,044.10