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 $212.61   6.220%   $225.8343   $225.83   $225.85   $225.80  
  Purchase #2 $230.28   6.626%   $245.5384   $245.54   $245.55   $245.50  
  Purchase #3 $74.81   5.287%   $78.7652   $78.77   $78.75   $78.80  
  Purchase #4 $246.93   5.595%   $260.7457   $260.75   $260.75   $260.70  
  Purchase #5 $98.54   6.782%   $105.223   $105.22   $105.20   $105.20  
  Purchase #6 $6.86   12.538%   $7.7201   $7.72   $7.70   $7.70  
  Purchase #7 $96.41   6.750%   $102.9177   $102.92   $102.90   $102.90  
  7 purchase totals = $966.44       $1,026.7444   $1,026.75   $1,026.70   $1,026.60