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	$93.42	7.533%	$100.4573	$100.46	$100.45	$100.50
Purchase #2	$116.48	13.705%	$132.4436	$132.44	$132.45	$132.40
Purchase #3	$19.88	12.577%	$22.3803	$22.38	$22.40	$22.40
Purchase #4	$103.55	7.718%	$111.542	$111.54	$111.55	$111.50
Purchase #5	$58.96	13.633%	$66.998	$67.00	$67.00	$67.00
Purchase #6	$137.85	4.293%	$143.7679	$143.77	$143.75	$143.80
Purchase #7	$160.54	5.307%	$169.0599	$169.06	$169.05	$169.10
7 purchase totals =	$690.68		$746.6490	$746.65	$746.65	$746.70