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	$199.63	8.116%	$215.832	$215.83	$215.85	$215.80
Purchase #2	$42.85	6.222%	$45.5161	$45.52	$45.50	$45.50
Purchase #3	$92.54	13.522%	$105.0533	$105.05	$105.05	$105.10
Purchase #4	$43.31	8.595%	$47.0325	$47.03	$47.05	$47.00
Purchase #5	$79.81	4.264%	$83.2131	$83.21	$83.20	$83.20
Purchase #6	$137.28	13.679%	$156.0585	$156.06	$156.05	$156.10
Purchase #7	$209.96	12.789%	$236.8118	$236.81	$236.80	$236.80
7 purchase totals =	$805.38		$889.5173	$889.51	$889.50	$889.50