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	$25.99	6.738%	$27.7412	$27.74	$27.75	$27.70
Purchase #2	$7.61	3.228%	$7.8557	$7.86	$7.85	$7.90
Purchase #3	$80.39	7.193%	$86.1725	$86.17	$86.15	$86.20
Purchase #4	$77.97	13.536%	$88.524	$88.52	$88.50	$88.50
Purchase #5	$87.96	13.719%	$100.0272	$100.03	$100.05	$100.00
Purchase #6	$10.60	8.141%	$11.4629	$11.46	$11.45	$11.50
Purchase #7	$64.54	12.492%	$72.6023	$72.60	$72.60	$72.60
7 purchase totals =	$355.06		$394.3858	$394.38	$394.35	$394.40