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	$127.83	5.249%	$134.5398	$134.54	$134.55	$134.50
Purchase #2	$48.85	11.562%	$54.498	$54.50	$54.50	$54.50
Purchase #3	$215.90	3.646%	$223.7717	$223.77	$223.75	$223.80
Purchase #4	$29.37	7.626%	$31.6098	$31.61	$31.60	$31.60
Purchase #5	$62.47	13.587%	$70.9578	$70.96	$70.95	$71.00
Purchase #6	$40.27	3.176%	$41.549	$41.55	$41.55	$41.50
Purchase #7	$127.31	11.387%	$141.8068	$141.81	$141.80	$141.80
7 purchase totals =	$652.00		$698.7329	$698.74	$698.70	$698.70