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 $24.38   6.807%   $26.0395   $26.04   $26.05   $26.00  
  Purchase #2 $247.32   5.152%   $260.0619   $260.06   $260.05   $260.10  
  Purchase #3 $223.79   8.654%   $243.1568   $243.16   $243.15   $243.20  
  Purchase #4 $55.55   9.514%   $60.835   $60.84   $60.85   $60.80  
  Purchase #5 $247.53   11.588%   $276.2138   $276.21   $276.20   $276.20  
  Purchase #6 $232.51   7.376%   $249.6599   $249.66   $249.65   $249.70  
  Purchase #7 $16.34   5.530%   $17.2436   $17.24   $17.25   $17.20  
  7 purchase totals = $1,047.42       $1,133.2105   $1,133.21   $1,133.20   $1,133.20