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	$69.67	12.654%	$78.486	$78.49	$78.50	$78.50
Purchase #2	$87.96	4.236%	$91.686	$91.69	$91.70	$91.70
Purchase #3	$5.41	3.604%	$5.605	$5.61	$5.60	$5.60
Purchase #4	$90.85	10.348%	$100.2512	$100.25	$100.25	$100.30
Purchase #5	$186.98	13.603%	$212.4149	$212.41	$212.40	$212.40
Purchase #6	$93.32	8.804%	$101.5359	$101.54	$101.55	$101.50
Purchase #7	$129.64	5.389%	$136.6263	$136.63	$136.65	$136.60
7 purchase totals =	$663.83		$726.6053	$726.62	$726.65	$726.60