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	$86.88	6.577%	$92.5941	$92.59	$92.60	$92.60
Purchase #2	$146.82	5.185%	$154.4326	$154.43	$154.45	$154.40
Purchase #3	$60.82	3.403%	$62.8897	$62.89	$62.90	$62.90
Purchase #4	$85.35	9.497%	$93.4557	$93.46	$93.45	$93.50
Purchase #5	$45.81	8.133%	$49.5357	$49.54	$49.55	$49.50
Purchase #6	$81.32	5.339%	$85.6617	$85.66	$85.65	$85.70
Purchase #7	$174.90	3.181%	$180.4636	$180.46	$180.45	$180.50
7 purchase totals =	$681.90		$719.0331	$719.03	$719.05	$719.10