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	$43.78	10.629%	$48.4334	$48.43	$48.45	$48.40
Purchase #2	$40.76	8.303%	$44.1443	$44.14	$44.15	$44.10
Purchase #3	$100.55	10.854%	$111.4637	$111.46	$111.45	$111.50
Purchase #4	$214.46	10.546%	$237.077	$237.08	$237.10	$237.10
Purchase #5	$140.48	5.846%	$148.6925	$148.69	$148.70	$148.70
Purchase #6	$45.49	12.203%	$51.0411	$51.04	$51.05	$51.00
Purchase #7	$112.27	3.805%	$116.5419	$116.54	$116.55	$116.50
7 purchase totals =	$697.79		$757.3939	$757.38	$757.45	$757.30