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	$51.94	6.540%	$55.3369	$55.34	$55.35	$55.30
Purchase #2	$183.38	8.462%	$198.8976	$198.90	$198.90	$198.90
Purchase #3	$149.38	6.406%	$158.9493	$158.95	$158.95	$158.90
Purchase #4	$64.88	4.623%	$67.8794	$67.88	$67.90	$67.90
Purchase #5	$228.45	4.459%	$238.6366	$238.64	$238.65	$238.60
Purchase #6	$177.75	12.843%	$200.5784	$200.58	$200.60	$200.60
Purchase #7	$143.84	3.258%	$148.5263	$148.53	$148.55	$148.50
7 purchase totals =	$999.62		$1,068.8045	$1,068.82	$1,068.90	$1,068.70