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	$58.27	6.504%	$62.0599	$62.06	$62.05	$62.10
Purchase #2	$84.76	5.696%	$89.5879	$89.59	$89.60	$89.60
Purchase #3	$126.58	5.558%	$133.6153	$133.62	$133.60	$133.60
Purchase #4	$72.60	13.618%	$82.4867	$82.49	$82.50	$82.50
Purchase #5	$42.70	6.443%	$45.4512	$45.45	$45.45	$45.50
Purchase #6	$134.35	7.573%	$144.5243	$144.52	$144.50	$144.50
Purchase #7	$175.27	8.298%	$189.8139	$189.81	$189.80	$189.80
7 purchase totals =	$694.53		$747.5392	$747.54	$747.50	$747.60