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	$215.90	10.680%	$238.9581	$238.96	$238.95	$239.00
Purchase #2	$58.70	4.328%	$61.2405	$61.24	$61.25	$61.20
Purchase #3	$72.89	7.684%	$78.4909	$78.49	$78.50	$78.50
Purchase #4	$42.76	6.105%	$45.3705	$45.37	$45.35	$45.40
Purchase #5	$225.50	5.455%	$237.801	$237.80	$237.80	$237.80
Purchase #6	$226.48	8.798%	$246.4057	$246.41	$246.40	$246.40
Purchase #7	$59.62	5.124%	$62.6749	$62.67	$62.65	$62.70
7 purchase totals =	$901.85		$970.9416	$970.94	$970.90	$971.00