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	$188.46	13.870%	$214.5994	$214.60	$214.60	$214.60
Purchase #2	$179.67	11.566%	$200.4506	$200.45	$200.45	$200.50
Purchase #3	$241.43	9.543%	$264.4697	$264.47	$264.45	$264.50
Purchase #4	$102.30	7.358%	$109.8272	$109.83	$109.85	$109.80
Purchase #5	$13.75	3.124%	$14.1796	$14.18	$14.20	$14.20
Purchase #6	$182.44	11.215%	$202.9006	$202.90	$202.90	$202.90
Purchase #7	$39.94	8.733%	$43.428	$43.43	$43.45	$43.40
7 purchase totals =	$947.99		$1,049.8551	$1,049.86	$1,049.90	$1,049.90