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	$177.45	10.786%	$196.5898	$196.59	$196.60	$196.60
Purchase #2	$118.97	8.541%	$129.1312	$129.13	$129.15	$129.10
Purchase #3	$144.69	5.458%	$152.5872	$152.59	$152.60	$152.60
Purchase #4	$128.95	13.185%	$145.9521	$145.95	$145.95	$146.00
Purchase #5	$56.72	9.446%	$62.0778	$62.08	$62.10	$62.10
Purchase #6	$76.70	4.494%	$80.1469	$80.15	$80.15	$80.10
Purchase #7	$59.34	8.866%	$64.6011	$64.60	$64.60	$64.60
7 purchase totals =	$762.82		$831.0861	$831.09	$831.15	$831.10