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	$126.41	6.330%	$134.4118	$134.41	$134.40	$134.40
Purchase #2	$241.85	5.774%	$255.8144	$255.81	$255.80	$255.80
Purchase #3	$142.75	11.665%	$159.4018	$159.40	$159.40	$159.40
Purchase #4	$165.52	7.544%	$178.0068	$178.01	$178.00	$178.00
Purchase #5	$35.93	7.225%	$38.5259	$38.53	$38.55	$38.50
Purchase #6	$159.70	3.632%	$165.5003	$165.50	$165.50	$165.50
Purchase #7	$143.40	5.182%	$150.831	$150.83	$150.85	$150.80
7 purchase totals =	$1,015.56		$1,082.4920	$1,082.49	$1,082.50	$1,082.40