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	$39.89	8.413%	$43.2459	$43.25	$43.25	$43.20
Purchase #2	$97.95	13.735%	$111.4034	$111.40	$111.40	$111.40
Purchase #3	$169.87	7.340%	$182.3385	$182.34	$182.35	$182.30
Purchase #4	$126.73	6.410%	$134.8534	$134.85	$134.85	$134.90
Purchase #5	$201.93	10.363%	$222.856	$222.86	$222.85	$222.90
Purchase #6	$215.79	6.413%	$229.6286	$229.63	$229.65	$229.60
Purchase #7	$16.82	9.719%	$18.4547	$18.45	$18.45	$18.50
7 purchase totals =	$868.98		$942.7805	$942.78	$942.80	$942.80