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	$118.99	10.730%	$131.7576	$131.76	$131.75	$131.80
Purchase #2	$100.71	6.788%	$107.5462	$107.55	$107.55	$107.50
Purchase #3	$6.46	10.145%	$7.1154	$7.12	$7.10	$7.10
Purchase #4	$198.38	11.675%	$221.5409	$221.54	$221.55	$221.50
Purchase #5	$174.64	7.831%	$188.3161	$188.32	$188.30	$188.30
Purchase #6	$125.68	5.509%	$132.6037	$132.60	$132.60	$132.60
Purchase #7	$127.46	11.820%	$142.5258	$142.53	$142.55	$142.50
7 purchase totals =	$852.32		$931.4057	$931.42	$931.40	$931.30