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 $62.62   11.664%   $69.924   $69.92   $69.90   $69.90  
  Purchase #2 $219.36   12.874%   $247.6004   $247.60   $247.60   $247.60  
  Purchase #3 $104.26   11.863%   $116.6284   $116.63   $116.65   $116.60  
  Purchase #4 $200.97   7.320%   $215.681   $215.68   $215.70   $215.70  
  Purchase #5 $174.34   4.734%   $182.5933   $182.59   $182.60   $182.60  
  Purchase #6 $9.47   13.117%   $10.7122   $10.71   $10.70   $10.70  
  Purchase #7 $67.70   9.610%   $74.206   $74.21   $74.20   $74.20  
  7 purchase totals = $838.72       $917.3453   $917.34   $917.35   $917.30