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	$180.92	10.516%	$199.9455	$199.95	$199.95	$199.90
Purchase #2	$120.92	8.382%	$131.0555	$131.06	$131.05	$131.10
Purchase #3	$36.34	8.574%	$39.4558	$39.46	$39.45	$39.50
Purchase #4	$119.77	11.863%	$133.9783	$133.98	$134.00	$134.00
Purchase #5	$132.75	4.767%	$139.0782	$139.08	$139.10	$139.10
Purchase #6	$222.57	10.782%	$246.5675	$246.57	$246.55	$246.60
Purchase #7	$223.45	6.178%	$237.2547	$237.25	$237.25	$237.30
7 purchase totals =	$1,036.72		$1,127.3355	$1,127.35	$1,127.35	$1,127.50