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	$132.69	8.122%	$143.4671	$143.47	$143.45	$143.50
Purchase #2	$17.27	9.477%	$18.9067	$18.91	$18.90	$18.90
Purchase #3	$53.51	7.500%	$57.5233	$57.52	$57.50	$57.50
Purchase #4	$153.57	4.235%	$160.0737	$160.07	$160.05	$160.10
Purchase #5	$241.48	5.710%	$255.2685	$255.27	$255.25	$255.30
Purchase #6	$40.91	5.858%	$43.3065	$43.31	$43.30	$43.30
Purchase #7	$117.58	4.697%	$123.1027	$123.10	$123.10	$123.10
7 purchase totals =	$757.01		$801.6485	$801.65	$801.55	$801.70