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 $181.49   8.364%   $196.6698   $196.67   $196.65   $196.70  
  Purchase #2 $65.76   13.726%   $74.7862   $74.79   $74.80   $74.80  
  Purchase #3 $180.61   5.264%   $190.1173   $190.12   $190.10   $190.10  
  Purchase #4 $228.41   6.103%   $242.3499   $242.35   $242.35   $242.30  
  Purchase #5 $246.77   10.762%   $273.3274   $273.33   $273.35   $273.30  
  Purchase #6 $96.47   6.436%   $102.6788   $102.68   $102.70   $102.70  
  Purchase #7 $26.80   6.127%   $28.442   $28.44   $28.45   $28.40  
  7 purchase totals = $1,026.31       $1,108.3714   $1,108.38   $1,108.40   $1,108.30