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 $67.95   13.240%   $76.9466   $76.95   $76.95   $76.90  
  Purchase #2 $88.70   10.316%   $97.8503   $97.85   $97.85   $97.90  
  Purchase #3 $102.75   11.573%   $114.6413   $114.64   $114.65   $114.60  
  Purchase #4 $56.92   6.690%   $60.7279   $60.73   $60.75   $60.70  
  Purchase #5 $19.86   10.473%   $21.9399   $21.94   $21.95   $21.90  
  Purchase #6 $133.34   4.212%   $138.9563   $138.96   $138.95   $139.00  
  Purchase #7 $66.48   5.660%   $70.2428   $70.24   $70.25   $70.20  
  7 purchase totals = $536.00       $581.3051   $581.31   $581.35   $581.20