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	$208.62	6.610%	$222.4098	$222.41	$222.40	$222.40
Purchase #2	$181.52	8.451%	$196.8603	$196.86	$196.85	$196.90
Purchase #3	$199.51	7.174%	$213.8228	$213.82	$213.80	$213.80
Purchase #4	$97.71	6.151%	$103.7201	$103.72	$103.70	$103.70
Purchase #5	$38.97	8.706%	$42.3627	$42.36	$42.35	$42.40
Purchase #6	$191.36	12.481%	$215.2436	$215.24	$215.25	$215.20
Purchase #7	$44.83	5.176%	$47.1504	$47.15	$47.15	$47.20
7 purchase totals =	$962.52		$1,041.5697	$1,041.56	$1,041.50	$1,041.60