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	$205.55	9.649%	$225.3835	$225.38	$225.40	$225.40
Purchase #2	$201.87	5.562%	$213.098	$213.10	$213.10	$213.10
Purchase #3	$206.77	4.646%	$216.3765	$216.38	$216.40	$216.40
Purchase #4	$135.27	3.413%	$139.8868	$139.89	$139.90	$139.90
Purchase #5	$246.98	13.452%	$280.2037	$280.20	$280.20	$280.20
Purchase #6	$16.94	5.271%	$17.8329	$17.83	$17.85	$17.80
Purchase #7	$155.91	4.299%	$162.6126	$162.61	$162.60	$162.60
7 purchase totals =	$1,169.29		$1,255.3940	$1,255.39	$1,255.45	$1,255.40