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	$127.78	9.197%	$139.5319	$139.53	$139.55	$139.50
Purchase #2	$201.47	6.480%	$214.5253	$214.53	$214.55	$214.50
Purchase #3	$175.52	8.740%	$190.8604	$190.86	$190.85	$190.90
Purchase #4	$51.88	5.176%	$54.5653	$54.57	$54.55	$54.60
Purchase #5	$132.39	4.622%	$138.5091	$138.51	$138.50	$138.50
Purchase #6	$236.77	10.396%	$261.3846	$261.38	$261.40	$261.40
Purchase #7	$122.84	7.466%	$132.0112	$132.01	$132.00	$132.00
7 purchase totals =	$1,048.65		$1,131.3878	$1,131.39	$1,131.40	$1,131.40