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	$169.36	10.796%	$187.6441	$187.64	$187.65	$187.60
Purchase #2	$119.42	6.783%	$127.5203	$127.52	$127.50	$127.50
Purchase #3	$68.67	11.713%	$76.7133	$76.71	$76.70	$76.70
Purchase #4	$71.59	10.152%	$78.8578	$78.86	$78.85	$78.90
Purchase #5	$153.30	10.247%	$169.0087	$169.01	$169.00	$169.00
Purchase #6	$189.84	12.858%	$214.2496	$214.25	$214.25	$214.20
Purchase #7	$173.42	5.863%	$183.5876	$183.59	$183.60	$183.60
7 purchase totals =	$945.60		$1,037.5814	$1,037.58	$1,037.55	$1,037.50