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	$13.59	4.237%	$14.1658	$14.17	$14.15	$14.20
Purchase #2	$215.39	12.461%	$242.2297	$242.23	$242.25	$242.20
Purchase #3	$85.29	10.140%	$93.9384	$93.94	$93.95	$93.90
Purchase #4	$150.83	11.794%	$168.6189	$168.62	$168.60	$168.60
Purchase #5	$85.66	11.311%	$95.349	$95.35	$95.35	$95.30
Purchase #6	$86.28	5.300%	$90.8528	$90.85	$90.85	$90.90
Purchase #7	$185.84	6.630%	$198.1612	$198.16	$198.15	$198.20
7 purchase totals =	$822.88		$903.3158	$903.32	$903.30	$903.30