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	$204.46	4.352%	$213.3581	$213.36	$213.35	$213.40
Purchase #2	$148.99	13.367%	$168.9055	$168.91	$168.90	$168.90
Purchase #3	$179.65	5.535%	$189.5936	$189.59	$189.60	$189.60
Purchase #4	$176.31	6.291%	$187.4017	$187.40	$187.40	$187.40
Purchase #5	$207.48	9.665%	$227.5329	$227.53	$227.55	$227.50
Purchase #6	$39.85	6.209%	$42.3243	$42.32	$42.30	$42.30
Purchase #7	$37.58	3.523%	$38.9039	$38.90	$38.90	$38.90
7 purchase totals =	$994.32		$1,068.0200	$1,068.01	$1,068.00	$1,068.00