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	$161.60	9.280%	$176.5965	$176.60	$176.60	$176.60
Purchase #2	$227.53	5.166%	$239.2842	$239.28	$239.30	$239.30
Purchase #3	$69.61	12.189%	$78.0948	$78.09	$78.10	$78.10
Purchase #4	$176.98	4.734%	$185.3582	$185.36	$185.35	$185.40
Purchase #5	$12.47	7.293%	$13.3794	$13.38	$13.40	$13.40
Purchase #6	$155.51	11.652%	$173.63	$173.63	$173.65	$173.60
Purchase #7	$20.80	3.419%	$21.5112	$21.51	$21.50	$21.50
7 purchase totals =	$824.50		$887.8543	$887.85	$887.90	$887.90