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	$133.71	12.459%	$150.3689	$150.37	$150.35	$150.40
Purchase #2	$160.37	7.771%	$172.8324	$172.83	$172.85	$172.80
Purchase #3	$28.52	10.337%	$31.4681	$31.47	$31.45	$31.50
Purchase #4	$75.73	13.361%	$85.8483	$85.85	$85.85	$85.80
Purchase #5	$136.91	3.410%	$141.5786	$141.58	$141.60	$141.60
Purchase #6	$105.79	11.732%	$118.2013	$118.20	$118.20	$118.20
Purchase #7	$49.34	10.235%	$54.3899	$54.39	$54.40	$54.40
7 purchase totals =	$690.37		$754.6875	$754.69	$754.70	$754.70