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	$245.72	6.390%	$261.4215	$261.42	$261.40	$261.40
Purchase #2	$25.25	13.325%	$28.6146	$28.61	$28.60	$28.60
Purchase #3	$245.30	4.140%	$255.4554	$255.46	$255.45	$255.50
Purchase #4	$174.58	9.792%	$191.6749	$191.67	$191.65	$191.70
Purchase #5	$12.82	4.509%	$13.3981	$13.40	$13.40	$13.40
Purchase #6	$171.96	10.239%	$189.567	$189.57	$189.55	$189.60
Purchase #7	$123.90	9.399%	$135.5454	$135.55	$135.55	$135.50
7 purchase totals =	$999.53		$1,075.6769	$1,075.68	$1,075.60	$1,075.70