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	$199.31	9.197%	$217.6405	$217.64	$217.65	$217.60
Purchase #2	$103.43	7.694%	$111.3879	$111.39	$111.40	$111.40
Purchase #3	$250.67	12.643%	$282.3622	$282.36	$282.35	$282.40
Purchase #4	$60.59	4.835%	$63.5195	$63.52	$63.50	$63.50
Purchase #5	$218.68	3.806%	$227.003	$227.00	$227.00	$227.00
Purchase #6	$81.27	4.716%	$85.1027	$85.10	$85.10	$85.10
Purchase #7	$226.46	3.115%	$233.5142	$233.51	$233.50	$233.50
7 purchase totals =	$1,140.41		$1,220.5300	$1,220.52	$1,220.50	$1,220.50