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 $167.32   6.527%   $178.241   $178.24   $178.25   $178.20  
  Purchase #2 $209.99   9.317%   $229.5548   $229.55   $229.55   $229.60  
  Purchase #3 $68.39   12.508%   $76.9442   $76.94   $76.95   $76.90  
  Purchase #4 $247.48   11.465%   $275.8536   $275.85   $275.85   $275.90  
  Purchase #5 $228.48   9.361%   $249.868   $249.87   $249.85   $249.90  
  Purchase #6 $9.62   4.838%   $10.0854   $10.09   $10.10   $10.10  
  Purchase #7 $43.28   8.247%   $46.8493   $46.85   $46.85   $46.80  
  7 purchase totals = $974.56       $1,067.3963   $1,067.39   $1,067.40   $1,067.40