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	$38.94	11.318%	$43.3472	$43.35	$43.35	$43.30
Purchase #2	$82.37	3.288%	$85.0783	$85.08	$85.10	$85.10
Purchase #3	$81.31	4.745%	$85.1682	$85.17	$85.15	$85.20
Purchase #4	$73.66	5.271%	$77.5426	$77.54	$77.55	$77.50
Purchase #5	$197.77	9.863%	$217.2761	$217.28	$217.30	$217.30
Purchase #6	$14.74	7.357%	$15.8244	$15.82	$15.80	$15.80
Purchase #7	$45.43	12.149%	$50.9493	$50.95	$50.95	$50.90
7 purchase totals =	$534.22		$575.1861	$575.19	$575.20	$575.10