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	$118.89	7.363%	$127.6439	$127.64	$127.65	$127.60
Purchase #2	$45.83	3.559%	$47.4611	$47.46	$47.45	$47.50
Purchase #3	$136.72	12.565%	$153.8989	$153.90	$153.90	$153.90
Purchase #4	$219.49	7.562%	$236.0878	$236.09	$236.10	$236.10
Purchase #5	$61.94	12.332%	$69.5784	$69.58	$69.60	$69.60
Purchase #6	$51.60	4.749%	$54.0505	$54.05	$54.05	$54.10
Purchase #7	$200.60	4.128%	$208.8808	$208.88	$208.90	$208.90
7 purchase totals =	$835.07		$897.6014	$897.60	$897.65	$897.70