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 $246.99   5.696%   $261.0586   $261.06   $261.05   $261.10  
  Purchase #2 $42.85   8.665%   $46.563   $46.56   $46.55   $46.60  
  Purchase #3 $170.54   6.603%   $181.8008   $181.80   $181.80   $181.80  
  Purchase #4 $236.85   7.211%   $253.9293   $253.93   $253.95   $253.90  
  Purchase #5 $97.74   6.562%   $104.1537   $104.15   $104.15   $104.20  
  Purchase #6 $163.35   8.617%   $177.4259   $177.43   $177.45   $177.40  
  Purchase #7 $115.32   9.214%   $125.9456   $125.95   $125.95   $125.90  
  7 purchase totals = $1,073.64       $1,150.8769   $1,150.88   $1,150.90   $1,150.90