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	$224.86	13.445%	$255.0924	$255.09	$255.10	$255.10
Purchase #2	$196.39	13.686%	$223.2679	$223.27	$223.25	$223.30
Purchase #3	$50.50	6.829%	$53.9486	$53.95	$53.95	$53.90
Purchase #4	$52.83	9.197%	$57.6888	$57.69	$57.70	$57.70
Purchase #5	$160.34	4.659%	$167.8102	$167.81	$167.80	$167.80
Purchase #6	$113.91	3.535%	$117.9367	$117.94	$117.95	$117.90
Purchase #7	$90.65	12.167%	$101.6794	$101.68	$101.70	$101.70
7 purchase totals =	$889.48		$977.4240	$977.43	$977.45	$977.40