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	$82.64	8.728%	$89.8528	$89.85	$89.85	$89.90
Purchase #2	$79.49	6.223%	$84.4367	$84.44	$84.45	$84.40
Purchase #3	$177.64	5.569%	$187.5328	$187.53	$187.55	$187.50
Purchase #4	$124.92	11.679%	$139.5094	$139.51	$139.50	$139.50
Purchase #5	$242.56	6.577%	$258.5132	$258.51	$258.50	$258.50
Purchase #6	$176.57	5.203%	$185.7569	$185.76	$185.75	$185.80
Purchase #7	$75.58	8.320%	$81.8683	$81.87	$81.85	$81.90
7 purchase totals =	$959.40		$1,027.4701	$1,027.47	$1,027.45	$1,027.50