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	$177.73	10.591%	$196.5534	$196.55	$196.55	$196.60
Purchase #2	$155.84	8.213%	$168.6391	$168.64	$168.65	$168.60
Purchase #3	$164.87	6.496%	$175.58	$175.58	$175.60	$175.60
Purchase #4	$51.39	9.792%	$56.4221	$56.42	$56.40	$56.40
Purchase #5	$18.36	13.166%	$20.7773	$20.78	$20.80	$20.80
Purchase #6	$149.44	6.113%	$158.5753	$158.58	$158.60	$158.60
Purchase #7	$217.29	6.635%	$231.7072	$231.71	$231.70	$231.70
7 purchase totals =	$934.92		$1,008.2544	$1,008.26	$1,008.30	$1,008.30