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	$103.57	10.498%	$114.4428	$114.44	$114.45	$114.40
Purchase #2	$130.60	6.854%	$139.5513	$139.55	$139.55	$139.60
Purchase #3	$82.84	8.214%	$89.6445	$89.64	$89.65	$89.60
Purchase #4	$104.54	4.348%	$109.0854	$109.09	$109.10	$109.10
Purchase #5	$217.34	7.189%	$232.9646	$232.96	$232.95	$233.00
Purchase #6	$234.31	10.517%	$258.9524	$258.95	$258.95	$259.00
Purchase #7	$199.36	11.540%	$222.3661	$222.37	$222.35	$222.40
7 purchase totals =	$1,072.56		$1,167.0071	$1,167.00	$1,167.00	$1,167.10