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	$48.91	12.338%	$54.9445	$54.94	$54.95	$54.90
Purchase #2	$40.80	12.781%	$46.0146	$46.01	$46.00	$46.00
Purchase #3	$32.51	8.815%	$35.3758	$35.38	$35.40	$35.40
Purchase #4	$221.46	4.373%	$231.1444	$231.14	$231.15	$231.10
Purchase #5	$164.65	5.840%	$174.2656	$174.27	$174.25	$174.30
Purchase #6	$139.78	13.226%	$158.2673	$158.27	$158.25	$158.30
Purchase #7	$127.31	12.735%	$143.5229	$143.52	$143.50	$143.50
7 purchase totals =	$775.42		$843.5351	$843.53	$843.50	$843.50