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 $119.65   3.257%   $123.547   $123.55   $123.55   $123.50  
  Purchase #2 $206.94   9.630%   $226.8683   $226.87   $226.85   $226.90  
  Purchase #3 $234.65   3.857%   $243.7005   $243.70   $243.70   $243.70  
  Purchase #4 $238.81   11.353%   $265.9221   $265.92   $265.90   $265.90  
  Purchase #5 $37.49   7.480%   $40.2943   $40.29   $40.30   $40.30  
  Purchase #6 $246.66   13.552%   $280.0874   $280.09   $280.10   $280.10  
  Purchase #7 $79.75   4.247%   $83.137   $83.14   $83.15   $83.10  
  7 purchase totals = $1,163.95       $1,263.5566   $1,263.56   $1,263.55   $1,263.50