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	$111.52	13.407%	$126.4715	$126.47	$126.45	$126.50
Purchase #2	$198.81	8.296%	$215.3033	$215.30	$215.30	$215.30
Purchase #3	$166.52	10.754%	$184.4276	$184.43	$184.45	$184.40
Purchase #4	$123.60	6.726%	$131.9133	$131.91	$131.90	$131.90
Purchase #5	$51.92	9.297%	$56.747	$56.75	$56.75	$56.70
Purchase #6	$128.96	10.131%	$142.0249	$142.02	$142.00	$142.00
Purchase #7	$138.67	9.765%	$152.2111	$152.21	$152.20	$152.20
7 purchase totals =	$920.00		$1,009.0987	$1,009.09	$1,009.05	$1,009.00