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	$72.36	9.733%	$79.4028	$79.40	$79.40	$79.40
Purchase #2	$12.74	5.210%	$13.4038	$13.40	$13.40	$13.40
Purchase #3	$176.56	4.842%	$185.109	$185.11	$185.10	$185.10
Purchase #4	$65.32	10.797%	$72.3726	$72.37	$72.35	$72.40
Purchase #5	$136.40	4.709%	$142.8231	$142.82	$142.80	$142.80
Purchase #6	$68.74	5.136%	$72.2705	$72.27	$72.25	$72.30
Purchase #7	$144.90	5.651%	$153.0883	$153.09	$153.10	$153.10
7 purchase totals =	$677.02		$718.4701	$718.46	$718.40	$718.50