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	$247.25	3.750%	$256.5219	$256.52	$256.50	$256.50
Purchase #2	$68.98	12.626%	$77.6894	$77.69	$77.70	$77.70
Purchase #3	$146.58	5.614%	$154.809	$154.81	$154.80	$154.80
Purchase #4	$106.86	5.538%	$112.7779	$112.78	$112.80	$112.80
Purchase #5	$102.30	3.152%	$105.5245	$105.52	$105.50	$105.50
Purchase #6	$131.63	10.865%	$145.9316	$145.93	$145.95	$145.90
Purchase #7	$228.83	4.347%	$238.7772	$238.78	$238.80	$238.80
7 purchase totals =	$1,032.43		$1,092.0315	$1,092.03	$1,092.05	$1,092.00