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	$102.47	8.864%	$111.5529	$111.55	$111.55	$111.60
Purchase #2	$37.33	6.348%	$39.6997	$39.70	$39.70	$39.70
Purchase #3	$38.45	13.300%	$43.5639	$43.56	$43.55	$43.60
Purchase #4	$43.82	11.379%	$48.8063	$48.81	$48.80	$48.80
Purchase #5	$145.69	7.322%	$156.3574	$156.36	$156.35	$156.40
Purchase #6	$90.87	12.610%	$102.3287	$102.33	$102.35	$102.30
Purchase #7	$150.71	5.181%	$158.5183	$158.52	$158.50	$158.50
7 purchase totals =	$609.34		$660.8272	$660.83	$660.80	$660.90