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 $247.81   7.328%   $265.9695   $265.97   $265.95   $266.00  
  Purchase #2 $125.89   11.716%   $140.6393   $140.64   $140.65   $140.60  
  Purchase #3 $27.69   10.515%   $30.6016   $30.60   $30.60   $30.60  
  Purchase #4 $79.68   5.396%   $83.9795   $83.98   $84.00   $84.00  
  Purchase #5 $232.51   4.800%   $243.6705   $243.67   $243.65   $243.70  
  Purchase #6 $135.49   9.270%   $148.0499   $148.05   $148.05   $148.00  
  Purchase #7 $178.69   6.166%   $189.708   $189.71   $189.70   $189.70  
  7 purchase totals = $1,027.76       $1,102.6183   $1,102.62   $1,102.60   $1,102.60