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	$51.81	11.531%	$57.7842	$57.78	$57.80	$57.80
Purchase #2	$135.53	11.780%	$151.4954	$151.50	$151.50	$151.50
Purchase #3	$150.31	11.719%	$167.9248	$167.92	$167.90	$167.90
Purchase #4	$14.96	8.869%	$16.2868	$16.29	$16.30	$16.30
Purchase #5	$192.53	5.634%	$203.3771	$203.38	$203.40	$203.40
Purchase #6	$63.92	4.194%	$66.6008	$66.60	$66.60	$66.60
Purchase #7	$198.86	11.667%	$222.061	$222.06	$222.05	$222.10
7 purchase totals =	$807.92		$885.5301	$885.53	$885.55	$885.60