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	$78.39	9.525%	$85.8566	$85.86	$85.85	$85.90
Purchase #2	$114.25	12.818%	$128.8946	$128.89	$128.90	$128.90
Purchase #3	$90.78	6.806%	$96.9585	$96.96	$96.95	$97.00
Purchase #4	$209.81	13.723%	$238.6022	$238.60	$238.60	$238.60
Purchase #5	$46.25	8.293%	$50.0855	$50.09	$50.10	$50.10
Purchase #6	$24.64	3.715%	$25.5554	$25.56	$25.55	$25.60
Purchase #7	$157.92	13.125%	$178.647	$178.65	$178.65	$178.60
7 purchase totals =	$722.04		$804.5998	$804.61	$804.60	$804.70