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	$132.45	7.622%	$142.5453	$142.55	$142.55	$142.50
Purchase #2	$42.34	9.697%	$46.4457	$46.45	$46.45	$46.40
Purchase #3	$93.81	7.422%	$100.7726	$100.77	$100.75	$100.80
Purchase #4	$188.42	4.639%	$197.1608	$197.16	$197.15	$197.20
Purchase #5	$100.73	11.153%	$111.9644	$111.96	$111.95	$112.00
Purchase #6	$36.84	9.438%	$40.317	$40.32	$40.30	$40.30
Purchase #7	$162.82	9.241%	$177.8662	$177.87	$177.85	$177.90
7 purchase totals =	$757.41		$817.0720	$817.08	$817.00	$817.10