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	$152.42	11.159%	$169.4285	$169.43	$169.45	$169.40
Purchase #2	$144.94	13.447%	$164.4301	$164.43	$164.45	$164.40
Purchase #3	$29.76	10.396%	$32.8538	$32.85	$32.85	$32.90
Purchase #4	$49.89	13.349%	$56.5498	$56.55	$56.55	$56.50
Purchase #5	$19.78	5.255%	$20.8194	$20.82	$20.80	$20.80
Purchase #6	$136.39	12.161%	$152.9764	$152.98	$153.00	$153.00
Purchase #7	$249.45	9.405%	$272.9108	$272.91	$272.90	$272.90
7 purchase totals =	$782.63		$869.9688	$869.97	$870.00	$869.90