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 $168.89   3.742%   $175.2099   $175.21   $175.20   $175.20  
  Purchase #2 $115.87   9.158%   $126.4814   $126.48   $126.50   $126.50  
  Purchase #3 $17.38   6.190%   $18.4558   $18.46   $18.45   $18.50  
  Purchase #4 $53.85   7.587%   $57.9356   $57.94   $57.95   $57.90  
  Purchase #5 $149.56   3.378%   $154.6121   $154.61   $154.60   $154.60  
  Purchase #6 $99.81   11.116%   $110.9049   $110.90   $110.90   $110.90  
  Purchase #7 $199.90   8.493%   $216.8775   $216.88   $216.90   $216.90  
  7 purchase totals = $805.26       $860.4772   $860.48   $860.50   $860.50