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	$245.52	10.707%	$271.8078	$271.81	$271.80	$271.80
Purchase #2	$16.40	11.492%	$18.2847	$18.28	$18.30	$18.30
Purchase #3	$160.78	4.622%	$168.2113	$168.21	$168.20	$168.20
Purchase #4	$166.83	3.542%	$172.7391	$172.74	$172.75	$172.70
Purchase #5	$82.46	8.676%	$89.6142	$89.61	$89.60	$89.60
Purchase #6	$173.80	7.605%	$187.0175	$187.02	$187.00	$187.00
Purchase #7	$36.71	4.205%	$38.2537	$38.25	$38.25	$38.30
7 purchase totals =	$882.50		$945.9283	$945.92	$945.90	$945.90