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	$208.43	4.347%	$217.4905	$217.49	$217.50	$217.50
Purchase #2	$103.87	9.661%	$113.9049	$113.90	$113.90	$113.90
Purchase #3	$152.32	13.714%	$173.2092	$173.21	$173.20	$173.20
Purchase #4	$201.84	6.699%	$215.3613	$215.36	$215.35	$215.40
Purchase #5	$12.69	3.496%	$13.1336	$13.13	$13.15	$13.10
Purchase #6	$83.63	13.116%	$94.5989	$94.60	$94.60	$94.60
Purchase #7	$150.72	9.161%	$164.5275	$164.53	$164.55	$164.50
7 purchase totals =	$913.50		$992.2259	$992.22	$992.25	$992.20