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 $248.32   5.438%   $261.8236   $261.82   $261.80   $261.80  
  Purchase #2 $201.67   5.349%   $212.4573   $212.46   $212.45   $212.50  
  Purchase #3 $126.96   9.508%   $139.0314   $139.03   $139.05   $139.00  
  Purchase #4 $118.45   5.345%   $124.7812   $124.78   $124.80   $124.80  
  Purchase #5 $210.65   6.315%   $223.9525   $223.95   $223.95   $224.00  
  Purchase #6 $199.29   4.227%   $207.714   $207.71   $207.70   $207.70  
  Purchase #7 $58.81   12.644%   $66.2459   $66.25   $66.25   $66.20  
  7 purchase totals = $1,164.15       $1,236.0059   $1,236.00   $1,236.00   $1,236.00