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	$116.82	13.366%	$132.4342	$132.43	$132.45	$132.40
Purchase #2	$103.43	11.850%	$115.6865	$115.69	$115.70	$115.70
Purchase #3	$94.69	11.315%	$105.4042	$105.40	$105.40	$105.40
Purchase #4	$6.89	11.194%	$7.6613	$7.66	$7.65	$7.70
Purchase #5	$109.72	9.381%	$120.0128	$120.01	$120.00	$120.00
Purchase #6	$52.35	4.238%	$54.5686	$54.57	$54.55	$54.60
Purchase #7	$17.42	9.162%	$19.016	$19.02	$19.00	$19.00
7 purchase totals =	$501.32		$554.7836	$554.78	$554.75	$554.80