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	$93.85	11.232%	$104.3912	$104.39	$104.40	$104.40
Purchase #2	$161.96	3.779%	$168.0805	$168.08	$168.10	$168.10
Purchase #3	$109.79	7.198%	$117.6927	$117.69	$117.70	$117.70
Purchase #4	$153.63	12.557%	$172.9213	$172.92	$172.90	$172.90
Purchase #5	$186.50	7.262%	$200.0436	$200.04	$200.05	$200.00
Purchase #6	$140.29	12.746%	$158.1714	$158.17	$158.15	$158.20
Purchase #7	$86.63	9.583%	$94.9318	$94.93	$94.95	$94.90
7 purchase totals =	$932.65		$1,016.2325	$1,016.22	$1,016.25	$1,016.20