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	$69.31	4.693%	$72.5627	$72.56	$72.55	$72.60
Purchase #2	$103.73	13.636%	$117.8746	$117.87	$117.85	$117.90
Purchase #3	$129.28	13.371%	$146.566	$146.57	$146.55	$146.60
Purchase #4	$244.68	12.582%	$275.4656	$275.47	$275.45	$275.50
Purchase #5	$38.68	12.170%	$43.3874	$43.39	$43.40	$43.40
Purchase #6	$31.61	9.302%	$34.5504	$34.55	$34.55	$34.60
Purchase #7	$25.42	8.380%	$27.5502	$27.55	$27.55	$27.60
7 purchase totals =	$642.71		$717.9569	$717.96	$717.90	$718.20