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	$217.93	9.480%	$238.5898	$238.59	$238.60	$238.60
Purchase #2	$207.55	9.716%	$227.7156	$227.72	$227.70	$227.70
Purchase #3	$136.38	12.182%	$152.9938	$152.99	$153.00	$153.00
Purchase #4	$90.31	13.152%	$102.1876	$102.19	$102.20	$102.20
Purchase #5	$87.52	3.387%	$90.4843	$90.48	$90.50	$90.50
Purchase #6	$156.97	3.830%	$162.982	$162.98	$163.00	$163.00
Purchase #7	$64.28	12.827%	$72.5252	$72.53	$72.55	$72.50
7 purchase totals =	$960.94		$1,047.4783	$1,047.48	$1,047.55	$1,047.50