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 $87.33   8.742%   $94.9644   $94.96   $94.95   $95.00  
  Purchase #2 $229.38   6.824%   $245.0329   $245.03   $245.05   $245.00  
  Purchase #3 $242.29   4.165%   $252.3814   $252.38   $252.40   $252.40  
  Purchase #4 $6.58   4.365%   $6.8672   $6.87   $6.85   $6.90  
  Purchase #5 $32.98   8.154%   $35.6692   $35.67   $35.65   $35.70  
  Purchase #6 $112.92   8.863%   $122.9281   $122.93   $122.95   $122.90  
  Purchase #7 $139.60   10.367%   $154.0723   $154.07   $154.05   $154.10  
  7 purchase totals = $851.08       $911.9155   $911.91   $911.90   $912.00