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	$62.46	4.869%	$65.5012	$65.50	$65.50	$65.50
Purchase #2	$165.35	6.722%	$176.4648	$176.46	$176.45	$176.50
Purchase #3	$40.56	3.185%	$41.8518	$41.85	$41.85	$41.90
Purchase #4	$122.34	4.390%	$127.7107	$127.71	$127.70	$127.70
Purchase #5	$116.57	13.853%	$132.7184	$132.72	$132.70	$132.70
Purchase #6	$146.99	12.195%	$164.9154	$164.92	$164.90	$164.90
Purchase #7	$97.93	13.609%	$111.2573	$111.26	$111.25	$111.30
7 purchase totals =	$752.20		$820.4196	$820.42	$820.35	$820.50