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	$49.81	11.120%	$55.3489	$55.35	$55.35	$55.30
Purchase #2	$7.57	4.329%	$7.8977	$7.90	$7.90	$7.90
Purchase #3	$57.96	9.237%	$63.3138	$63.31	$63.30	$63.30
Purchase #4	$115.94	13.371%	$131.4423	$131.44	$131.45	$131.40
Purchase #5	$106.49	5.153%	$111.9774	$111.98	$112.00	$112.00
Purchase #6	$242.82	4.752%	$254.3588	$254.36	$254.35	$254.40
Purchase #7	$104.82	8.735%	$113.976	$113.98	$114.00	$114.00
7 purchase totals =	$685.41		$738.3149	$738.32	$738.35	$738.30