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	$183.99	3.558%	$190.5364	$190.54	$190.55	$190.50
Purchase #2	$133.35	4.430%	$139.2574	$139.26	$139.25	$139.30
Purchase #3	$203.70	11.178%	$226.4696	$226.47	$226.45	$226.50
Purchase #4	$40.34	13.626%	$45.8367	$45.84	$45.85	$45.80
Purchase #5	$62.29	7.195%	$66.7718	$66.77	$66.75	$66.80
Purchase #6	$45.32	12.393%	$50.9365	$50.94	$50.95	$50.90
Purchase #7	$200.52	4.508%	$209.5594	$209.56	$209.55	$209.60
7 purchase totals =	$869.51		$929.3678	$929.38	$929.35	$929.40