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	$79.32	5.622%	$83.7794	$83.78	$83.80	$83.80
Purchase #2	$181.89	13.544%	$206.5252	$206.53	$206.55	$206.50
Purchase #3	$206.53	9.347%	$225.8344	$225.83	$225.85	$225.80
Purchase #4	$200.57	11.615%	$223.8662	$223.87	$223.85	$223.90
Purchase #5	$196.59	8.351%	$213.0072	$213.01	$213.00	$213.00
Purchase #6	$39.91	8.407%	$43.2652	$43.27	$43.25	$43.30
Purchase #7	$192.54	8.252%	$208.4284	$208.43	$208.45	$208.40
7 purchase totals =	$1,097.35		$1,204.7060	$1,204.72	$1,204.75	$1,204.70