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	$156.39	7.147%	$167.5672	$167.57	$167.55	$167.60
Purchase #2	$215.27	10.859%	$238.6462	$238.65	$238.65	$238.60
Purchase #3	$210.59	4.124%	$219.2747	$219.27	$219.25	$219.30
Purchase #4	$192.51	13.205%	$217.9309	$217.93	$217.95	$217.90
Purchase #5	$68.95	13.162%	$78.0252	$78.03	$78.05	$78.00
Purchase #6	$169.81	3.812%	$176.2832	$176.28	$176.30	$176.30
Purchase #7	$123.67	13.647%	$140.5472	$140.55	$140.55	$140.50
7 purchase totals =	$1,137.19		$1,238.2746	$1,238.28	$1,238.30	$1,238.20