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	$12.61	10.541%	$13.9392	$13.94	$13.95	$13.90
Purchase #2	$86.82	3.769%	$90.0922	$90.09	$90.10	$90.10
Purchase #3	$66.78	9.444%	$73.0867	$73.09	$73.10	$73.10
Purchase #4	$74.90	5.241%	$78.8255	$78.83	$78.85	$78.80
Purchase #5	$172.44	5.810%	$182.4588	$182.46	$182.45	$182.50
Purchase #6	$9.45	13.143%	$10.692	$10.69	$10.70	$10.70
Purchase #7	$138.56	10.762%	$153.4718	$153.47	$153.45	$153.50
7 purchase totals =	$561.56		$602.5662	$602.57	$602.60	$602.60