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	$137.29	8.409%	$148.8347	$148.83	$148.85	$148.80
Purchase #2	$77.64	11.314%	$86.4242	$86.42	$86.40	$86.40
Purchase #3	$61.81	5.182%	$65.013	$65.01	$65.00	$65.00
Purchase #4	$143.37	5.167%	$150.7779	$150.78	$150.80	$150.80
Purchase #5	$57.54	8.542%	$62.4551	$62.46	$62.45	$62.50
Purchase #6	$135.82	10.550%	$150.149	$150.15	$150.15	$150.10
Purchase #7	$225.78	10.465%	$249.4079	$249.41	$249.40	$249.40
7 purchase totals =	$839.25		$913.0618	$913.06	$913.05	$913.00