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	$83.75	3.357%	$86.5615	$86.56	$86.55	$86.60
Purchase #2	$145.45	10.312%	$160.4488	$160.45	$160.45	$160.40
Purchase #3	$215.44	10.854%	$238.8239	$238.82	$238.80	$238.80
Purchase #4	$225.69	13.441%	$256.025	$256.03	$256.05	$256.00
Purchase #5	$153.52	9.788%	$168.5465	$168.55	$168.55	$168.50
Purchase #6	$91.58	13.345%	$103.8014	$103.80	$103.80	$103.80
Purchase #7	$77.98	8.751%	$84.804	$84.80	$84.80	$84.80
7 purchase totals =	$993.41		$1,099.0111	$1,099.01	$1,099.00	$1,098.90