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	$126.41	4.808%	$132.4878	$132.49	$132.50	$132.50
Purchase #2	$118.39	7.306%	$127.0396	$127.04	$127.05	$127.00
Purchase #3	$239.66	13.599%	$272.2514	$272.25	$272.25	$272.30
Purchase #4	$110.68	3.384%	$114.4254	$114.43	$114.45	$114.40
Purchase #5	$99.51	13.688%	$113.1309	$113.13	$113.15	$113.10
Purchase #6	$41.86	10.854%	$46.4035	$46.40	$46.40	$46.40
Purchase #7	$59.55	6.777%	$63.5857	$63.59	$63.60	$63.60
7 purchase totals =	$796.06		$869.3243	$869.33	$869.40	$869.30