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	$140.47	10.645%	$155.423	$155.42	$155.40	$155.40
Purchase #2	$85.51	11.151%	$95.0452	$95.05	$95.05	$95.00
Purchase #3	$112.99	11.334%	$125.7963	$125.80	$125.80	$125.80
Purchase #4	$168.35	3.711%	$174.5975	$174.60	$174.60	$174.60
Purchase #5	$76.85	7.604%	$82.6937	$82.69	$82.70	$82.70
Purchase #6	$78.97	4.570%	$82.5789	$82.58	$82.60	$82.60
Purchase #7	$143.45	3.777%	$148.8681	$148.87	$148.85	$148.90
7 purchase totals =	$806.59		$865.0027	$865.01	$865.00	$865.00