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	$250.36	10.429%	$276.47	$276.47	$276.45	$276.50
Purchase #2	$76.32	4.853%	$80.0238	$80.02	$80.00	$80.00
Purchase #3	$54.37	4.748%	$56.9515	$56.95	$56.95	$57.00
Purchase #4	$58.76	4.624%	$61.4771	$61.48	$61.50	$61.50
Purchase #5	$212.94	9.737%	$233.674	$233.67	$233.65	$233.70
Purchase #6	$240.25	10.575%	$265.6564	$265.66	$265.65	$265.70
Purchase #7	$100.37	10.848%	$111.2581	$111.26	$111.25	$111.30
7 purchase totals =	$993.37		$1,085.5109	$1,085.51	$1,085.45	$1,085.70