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	$9.68	13.126%	$10.9506	$10.95	$10.95	$11.00
Purchase #2	$206.56	13.698%	$234.8546	$234.85	$234.85	$234.90
Purchase #3	$139.94	11.147%	$155.5391	$155.54	$155.55	$155.50
Purchase #4	$43.69	4.221%	$45.5342	$45.53	$45.55	$45.50
Purchase #5	$102.28	6.783%	$109.2177	$109.22	$109.20	$109.20
Purchase #6	$172.86	8.134%	$186.9204	$186.92	$186.90	$186.90
Purchase #7	$143.61	10.269%	$158.3573	$158.36	$158.35	$158.40
7 purchase totals =	$818.62		$901.3739	$901.37	$901.35	$901.40