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	$123.90	7.319%	$132.9682	$132.97	$132.95	$133.00
Purchase #2	$108.90	5.265%	$114.6336	$114.63	$114.65	$114.60
Purchase #3	$132.89	13.521%	$150.8581	$150.86	$150.85	$150.90
Purchase #4	$164.47	8.733%	$178.8332	$178.83	$178.85	$178.80
Purchase #5	$111.83	8.725%	$121.5872	$121.59	$121.60	$121.60
Purchase #6	$89.74	6.705%	$95.7571	$95.76	$95.75	$95.80
Purchase #7	$213.60	3.350%	$220.7556	$220.76	$220.75	$220.80
7 purchase totals =	$945.33		$1,015.3930	$1,015.40	$1,015.40	$1,015.50