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	$135.90	3.724%	$140.9609	$140.96	$140.95	$141.00
Purchase #2	$73.63	5.759%	$77.8704	$77.87	$77.85	$77.90
Purchase #3	$75.80	9.431%	$82.9487	$82.95	$82.95	$82.90
Purchase #4	$86.96	3.794%	$90.2593	$90.26	$90.25	$90.30
Purchase #5	$71.65	9.716%	$78.6115	$78.61	$78.60	$78.60
Purchase #6	$112.95	3.137%	$116.4932	$116.49	$116.50	$116.50
Purchase #7	$210.95	13.711%	$239.8734	$239.87	$239.85	$239.90
7 purchase totals =	$767.84		$827.0174	$827.01	$826.95	$827.10