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	$43.48	10.509%	$48.0493	$48.05	$48.05	$48.00
Purchase #2	$100.60	7.616%	$108.2617	$108.26	$108.25	$108.30
Purchase #3	$33.67	11.615%	$37.5808	$37.58	$37.60	$37.60
Purchase #4	$248.53	11.280%	$276.5642	$276.56	$276.55	$276.60
Purchase #5	$78.81	5.705%	$83.3061	$83.31	$83.30	$83.30
Purchase #6	$63.51	6.602%	$67.7029	$67.70	$67.70	$67.70
Purchase #7	$142.33	9.268%	$155.5211	$155.52	$155.50	$155.50
7 purchase totals =	$710.93		$776.9861	$776.98	$776.95	$777.00