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	$248.80	10.342%	$274.5309	$274.53	$274.55	$274.50
Purchase #2	$135.83	3.411%	$140.4632	$140.46	$140.45	$140.50
Purchase #3	$27.61	6.824%	$29.4941	$29.49	$29.50	$29.50
Purchase #4	$200.83	8.287%	$217.4728	$217.47	$217.45	$217.50
Purchase #5	$108.82	13.265%	$123.255	$123.26	$123.25	$123.30
Purchase #6	$50.52	7.389%	$54.2529	$54.25	$54.25	$54.30
Purchase #7	$197.40	11.808%	$220.709	$220.71	$220.70	$220.70
7 purchase totals =	$969.81		$1,060.1779	$1,060.17	$1,060.15	$1,060.30