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	$71.36	12.733%	$80.4463	$80.45	$80.45	$80.40
Purchase #2	$40.32	8.136%	$43.6004	$43.60	$43.60	$43.60
Purchase #3	$52.90	8.622%	$57.461	$57.46	$57.45	$57.50
Purchase #4	$220.47	9.697%	$241.849	$241.85	$241.85	$241.80
Purchase #5	$200.36	11.808%	$224.0185	$224.02	$224.00	$224.00
Purchase #6	$140.88	12.771%	$158.8718	$158.87	$158.85	$158.90
Purchase #7	$82.51	12.482%	$92.8089	$92.81	$92.80	$92.80
7 purchase totals =	$808.80		$899.0559	$899.06	$899.00	$899.00