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	$242.28	5.691%	$256.0682	$256.07	$256.05	$256.10
Purchase #2	$172.98	6.721%	$184.606	$184.61	$184.60	$184.60
Purchase #3	$17.72	3.264%	$18.2984	$18.30	$18.30	$18.30
Purchase #4	$123.95	5.546%	$130.8243	$130.82	$130.80	$130.80
Purchase #5	$169.92	10.340%	$187.4897	$187.49	$187.50	$187.50
Purchase #6	$39.77	6.687%	$42.4294	$42.43	$42.45	$42.40
Purchase #7	$180.99	13.455%	$205.3422	$205.34	$205.35	$205.30
7 purchase totals =	$947.61		$1,025.0582	$1,025.06	$1,025.05	$1,025.00