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 $71.75   6.833%   $76.6527   $76.65   $76.65   $76.70  
  Purchase #2 $150.71   7.848%   $162.5377   $162.54   $162.55   $162.50  
  Purchase #3 $11.53   7.671%   $12.4145   $12.41   $12.40   $12.40  
  Purchase #4 $89.70   3.128%   $92.5058   $92.51   $92.50   $92.50  
  Purchase #5 $83.88   11.309%   $93.366   $93.37   $93.35   $93.40  
  Purchase #6 $207.50   9.743%   $227.7167   $227.72   $227.70   $227.70  
  Purchase #7 $185.49   11.814%   $207.4038   $207.40   $207.40   $207.40  
  7 purchase totals = $800.56       $872.5972   $872.60   $872.55   $872.60