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	$231.34	3.298%	$238.9696	$238.97	$238.95	$239.00
Purchase #2	$69.68	4.103%	$72.539	$72.54	$72.55	$72.50
Purchase #3	$11.69	10.166%	$12.8784	$12.88	$12.90	$12.90
Purchase #4	$197.34	9.247%	$215.588	$215.59	$215.60	$215.60
Purchase #5	$62.71	8.691%	$68.1601	$68.16	$68.15	$68.20
Purchase #6	$122.37	8.333%	$132.5671	$132.57	$132.55	$132.60
Purchase #7	$246.59	10.664%	$272.8864	$272.89	$272.90	$272.90
7 purchase totals =	$941.72		$1,013.5886	$1,013.60	$1,013.60	$1,013.70