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	$69.50	3.811%	$72.1486	$72.15	$72.15	$72.10
Purchase #2	$48.44	12.193%	$54.3463	$54.35	$54.35	$54.30
Purchase #3	$102.89	9.604%	$112.7716	$112.77	$112.75	$112.80
Purchase #4	$62.80	5.228%	$66.0832	$66.08	$66.10	$66.10
Purchase #5	$141.35	10.658%	$156.4151	$156.42	$156.40	$156.40
Purchase #6	$131.57	13.696%	$149.5898	$149.59	$149.60	$149.60
Purchase #7	$246.54	11.215%	$274.1895	$274.19	$274.20	$274.20
7 purchase totals =	$803.09		$885.5441	$885.55	$885.55	$885.50