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	$157.69	8.831%	$171.6156	$171.62	$171.60	$171.60
Purchase #2	$43.76	7.641%	$47.1037	$47.10	$47.10	$47.10
Purchase #3	$84.77	4.429%	$88.5245	$88.52	$88.50	$88.50
Purchase #4	$208.80	6.262%	$221.8751	$221.88	$221.90	$221.90
Purchase #5	$237.79	7.355%	$255.2795	$255.28	$255.30	$255.30
Purchase #6	$121.77	7.792%	$131.2583	$131.26	$131.25	$131.30
Purchase #7	$169.83	8.238%	$183.8206	$183.82	$183.80	$183.80
7 purchase totals =	$1,024.41		$1,099.4773	$1,099.48	$1,099.45	$1,099.50