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	$49.75	10.373%	$54.9106	$54.91	$54.90	$54.90
Purchase #2	$208.94	8.209%	$226.0919	$226.09	$226.10	$226.10
Purchase #3	$81.88	9.806%	$89.9092	$89.91	$89.90	$89.90
Purchase #4	$119.51	6.330%	$127.075	$127.08	$127.10	$127.10
Purchase #5	$113.55	4.137%	$118.2476	$118.25	$118.25	$118.20
Purchase #6	$127.28	8.433%	$138.0135	$138.01	$138.00	$138.00
Purchase #7	$246.62	3.564%	$255.4095	$255.41	$255.40	$255.40
7 purchase totals =	$947.53		$1,009.6573	$1,009.66	$1,009.65	$1,009.60