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 $59.86   9.400%   $65.4868   $65.49   $65.50   $65.50  
  Purchase #2 $110.63   10.874%   $122.6599   $122.66   $122.65   $122.70  
  Purchase #3 $223.53   5.158%   $235.0597   $235.06   $235.05   $235.10  
  Purchase #4 $169.46   12.658%   $190.9102   $190.91   $190.90   $190.90  
  Purchase #5 $200.87   13.497%   $227.9814   $227.98   $228.00   $228.00  
  Purchase #6 $129.43   4.524%   $135.2854   $135.29   $135.30   $135.30  
  Purchase #7 $211.79   6.262%   $225.0523   $225.05   $225.05   $225.10  
  7 purchase totals = $1,105.57       $1,202.4357   $1,202.44   $1,202.45   $1,202.60