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	$168.97	8.173%	$182.7799	$182.78	$182.80	$182.80
Purchase #2	$43.39	4.208%	$45.2159	$45.22	$45.20	$45.20
Purchase #3	$100.82	10.669%	$111.5765	$111.58	$111.60	$111.60
Purchase #4	$128.40	10.756%	$142.2107	$142.21	$142.20	$142.20
Purchase #5	$215.97	10.371%	$238.3682	$238.37	$238.35	$238.40
Purchase #6	$201.78	3.733%	$209.3124	$209.31	$209.30	$209.30
Purchase #7	$44.96	10.696%	$49.7689	$49.77	$49.75	$49.80
7 purchase totals =	$904.29		$979.2325	$979.24	$979.20	$979.30