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 $78.36   9.212%   $85.5785   $85.58   $85.60   $85.60  
  Purchase #2 $250.76   7.154%   $268.6994   $268.70   $268.70   $268.70  
  Purchase #3 $89.36   6.551%   $95.214   $95.21   $95.20   $95.20  
  Purchase #4 $133.91   4.547%   $139.9989   $140.00   $140.00   $140.00  
  Purchase #5 $226.62   13.595%   $257.429   $257.43   $257.45   $257.40  
  Purchase #6 $217.79   12.786%   $245.6366   $245.64   $245.65   $245.60  
  Purchase #7 $11.45   8.635%   $12.4387   $12.44   $12.45   $12.40  
  7 purchase totals = $1,008.25       $1,104.9951   $1,105.00   $1,105.05   $1,104.90