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	$247.90	8.868%	$269.8838	$269.88	$269.90	$269.90
Purchase #2	$194.84	5.547%	$205.6478	$205.65	$205.65	$205.60
Purchase #3	$17.39	12.694%	$19.5975	$19.60	$19.60	$19.60
Purchase #4	$133.83	5.743%	$141.5159	$141.52	$141.50	$141.50
Purchase #5	$142.51	5.833%	$150.8226	$150.82	$150.80	$150.80
Purchase #6	$228.40	12.313%	$256.5229	$256.52	$256.50	$256.50
Purchase #7	$117.54	8.698%	$127.7636	$127.76	$127.75	$127.80
7 purchase totals =	$1,082.41		$1,171.7541	$1,171.75	$1,171.70	$1,171.70