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	$215.47	9.254%	$235.4096	$235.41	$235.40	$235.40
Purchase #2	$95.30	4.864%	$99.9354	$99.94	$99.95	$99.90
Purchase #3	$169.95	11.824%	$190.0449	$190.04	$190.05	$190.00
Purchase #4	$78.74	5.781%	$83.292	$83.29	$83.30	$83.30
Purchase #5	$52.34	4.186%	$54.531	$54.53	$54.55	$54.50
Purchase #6	$231.90	10.160%	$255.461	$255.46	$255.45	$255.50
Purchase #7	$100.83	13.477%	$114.4189	$114.42	$114.40	$114.40
7 purchase totals =	$944.53		$1,033.0928	$1,033.09	$1,033.10	$1,033.00