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	$40.63	10.283%	$44.808	$44.81	$44.80	$44.80
Purchase #2	$184.86	6.438%	$196.7613	$196.76	$196.75	$196.80
Purchase #3	$43.29	9.280%	$47.3073	$47.31	$47.30	$47.30
Purchase #4	$157.67	6.246%	$167.5181	$167.52	$167.50	$167.50
Purchase #5	$233.76	9.303%	$255.5067	$255.51	$255.50	$255.50
Purchase #6	$21.95	13.317%	$24.8731	$24.87	$24.85	$24.90
Purchase #7	$41.62	8.856%	$45.3059	$45.31	$45.30	$45.30
7 purchase totals =	$723.78		$782.0804	$782.09	$782.00	$782.10