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	$176.54	12.564%	$198.7205	$198.72	$198.70	$198.70
Purchase #2	$163.77	10.417%	$180.8299	$180.83	$180.85	$180.80
Purchase #3	$156.40	12.735%	$176.3175	$176.32	$176.30	$176.30
Purchase #4	$78.87	9.719%	$86.5354	$86.54	$86.55	$86.50
Purchase #5	$119.41	3.367%	$123.4305	$123.43	$123.45	$123.40
Purchase #6	$49.35	4.579%	$51.6097	$51.61	$51.60	$51.60
Purchase #7	$174.70	11.180%	$194.2315	$194.23	$194.25	$194.20
7 purchase totals =	$919.04		$1,011.6750	$1,011.68	$1,011.70	$1,011.50