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	$228.99	9.806%	$251.4448	$251.44	$251.45	$251.40
Purchase #2	$51.95	7.387%	$55.7875	$55.79	$55.80	$55.80
Purchase #3	$154.55	5.244%	$162.6546	$162.65	$162.65	$162.70
Purchase #4	$178.64	10.246%	$196.9435	$196.94	$196.95	$196.90
Purchase #5	$178.78	4.676%	$187.1398	$187.14	$187.15	$187.10
Purchase #6	$126.47	12.786%	$142.6405	$142.64	$142.65	$142.60
Purchase #7	$11.38	7.746%	$12.2615	$12.26	$12.25	$12.30
7 purchase totals =	$930.76		$1,008.8722	$1,008.86	$1,008.90	$1,008.80