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	$102.73	9.533%	$112.5233	$112.52	$112.50	$112.50
Purchase #2	$227.46	12.153%	$255.1032	$255.10	$255.10	$255.10
Purchase #3	$115.25	6.818%	$123.1077	$123.11	$123.10	$123.10
Purchase #4	$97.88	8.410%	$106.1117	$106.11	$106.10	$106.10
Purchase #5	$217.50	4.181%	$226.5937	$226.59	$226.60	$226.60
Purchase #6	$62.78	4.402%	$65.5436	$65.54	$65.55	$65.50
Purchase #7	$130.76	8.638%	$142.055	$142.06	$142.05	$142.10
7 purchase totals =	$954.36		$1,031.0382	$1,031.03	$1,031.00	$1,031.00