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	$182.84	12.404%	$205.5195	$205.52	$205.50	$205.50
Purchase #2	$194.61	11.778%	$217.5312	$217.53	$217.55	$217.50
Purchase #3	$102.58	9.243%	$112.0615	$112.06	$112.05	$112.10
Purchase #4	$235.82	12.734%	$265.8493	$265.85	$265.85	$265.80
Purchase #5	$17.72	10.128%	$19.5147	$19.51	$19.50	$19.50
Purchase #6	$245.72	8.479%	$266.5546	$266.55	$266.55	$266.60
Purchase #7	$86.54	9.203%	$94.5043	$94.50	$94.50	$94.50
7 purchase totals =	$1,065.83		$1,181.5351	$1,181.52	$1,181.50	$1,181.50