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 $24.92   3.756%   $25.856   $25.86   $25.85   $25.90  
  Purchase #2 $233.36   6.275%   $248.0033   $248.00   $248.00   $248.00  
  Purchase #3 $179.39   12.828%   $202.4021   $202.40   $202.40   $202.40  
  Purchase #4 $164.65   13.524%   $186.9173   $186.92   $186.90   $186.90  
  Purchase #5 $108.49   10.196%   $119.5516   $119.55   $119.55   $119.60  
  Purchase #6 $91.95   11.532%   $102.5537   $102.55   $102.55   $102.60  
  Purchase #7 $73.63   3.755%   $76.3948   $76.39   $76.40   $76.40  
  7 purchase totals = $876.39       $961.6788   $961.67   $961.65   $961.80