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	$162.90	3.628%	$168.81	$168.81	$168.80	$168.80
Purchase #2	$86.59	9.225%	$94.5779	$94.58	$94.60	$94.60
Purchase #3	$98.26	11.239%	$109.3034	$109.30	$109.30	$109.30
Purchase #4	$192.50	7.443%	$206.8278	$206.83	$206.85	$206.80
Purchase #5	$16.43	7.442%	$17.6527	$17.65	$17.65	$17.70
Purchase #6	$50.75	3.639%	$52.5968	$52.60	$52.60	$52.60
Purchase #7	$14.71	5.707%	$15.5495	$15.55	$15.55	$15.50
7 purchase totals =	$622.14		$665.3181	$665.32	$665.35	$665.30