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	$124.34	3.636%	$128.861	$128.86	$128.85	$128.90
Purchase #2	$230.97	10.665%	$255.603	$255.60	$255.60	$255.60
Purchase #3	$91.83	7.429%	$98.6521	$98.65	$98.65	$98.70
Purchase #4	$173.58	4.571%	$181.5143	$181.51	$181.50	$181.50
Purchase #5	$177.84	8.450%	$192.8675	$192.87	$192.85	$192.90
Purchase #6	$47.68	8.104%	$51.544	$51.54	$51.55	$51.50
Purchase #7	$113.25	13.342%	$128.3598	$128.36	$128.35	$128.40
7 purchase totals =	$959.49		$1,037.4017	$1,037.39	$1,037.35	$1,037.50