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 $61.53   9.869%   $67.6024   $67.60   $67.60   $67.60  
  Purchase #2 $175.32   13.615%   $199.1898   $199.19   $199.20   $199.20  
  Purchase #3 $50.81   7.716%   $54.7305   $54.73   $54.75   $54.70  
  Purchase #4 $119.56   5.531%   $126.1729   $126.17   $126.15   $126.20  
  Purchase #5 $58.35   10.206%   $64.3052   $64.31   $64.30   $64.30  
  Purchase #6 $196.94   6.246%   $209.2409   $209.24   $209.25   $209.20  
  Purchase #7 $216.91   4.433%   $226.5256   $226.53   $226.55   $226.50  
  7 purchase totals = $879.42       $947.7673   $947.77   $947.80   $947.70