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	$150.92	11.258%	$167.9106	$167.91	$167.90	$167.90
Purchase #2	$177.45	3.131%	$183.006	$183.01	$183.00	$183.00
Purchase #3	$161.41	4.276%	$168.3119	$168.31	$168.30	$168.30
Purchase #4	$126.61	4.810%	$132.6999	$132.70	$132.70	$132.70
Purchase #5	$131.40	5.736%	$138.9371	$138.94	$138.95	$138.90
Purchase #6	$105.76	5.765%	$111.8571	$111.86	$111.85	$111.90
Purchase #7	$130.45	3.385%	$134.8657	$134.87	$134.85	$134.90
7 purchase totals =	$984.00		$1,037.5883	$1,037.60	$1,037.55	$1,037.60