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	$45.32	8.586%	$49.2112	$49.21	$49.20	$49.20
Purchase #2	$37.82	11.719%	$42.2521	$42.25	$42.25	$42.30
Purchase #3	$241.39	5.176%	$253.8843	$253.88	$253.90	$253.90
Purchase #4	$113.64	10.710%	$125.8108	$125.81	$125.80	$125.80
Purchase #5	$118.49	7.792%	$127.7227	$127.72	$127.70	$127.70
Purchase #6	$238.28	12.242%	$267.4502	$267.45	$267.45	$267.50
Purchase #7	$17.47	12.132%	$19.5895	$19.59	$19.60	$19.60
7 purchase totals =	$812.41		$885.9208	$885.91	$885.90	$886.00