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	$80.25	6.562%	$85.516	$85.52	$85.50	$85.50
Purchase #2	$206.89	3.731%	$214.6091	$214.61	$214.60	$214.60
Purchase #3	$164.60	13.568%	$186.9329	$186.93	$186.95	$186.90
Purchase #4	$125.28	13.767%	$142.5273	$142.53	$142.55	$142.50
Purchase #5	$96.29	12.469%	$108.2964	$108.30	$108.30	$108.30
Purchase #6	$51.64	9.472%	$56.5313	$56.53	$56.55	$56.50
Purchase #7	$206.55	10.293%	$227.8102	$227.81	$227.80	$227.80
7 purchase totals =	$931.50		$1,022.2232	$1,022.23	$1,022.25	$1,022.10