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 $71.64   6.641%   $76.3976   $76.40   $76.40   $76.40  
  Purchase #2 $200.32   12.149%   $224.6569   $224.66   $224.65   $224.70  
  Purchase #3 $105.26   11.446%   $117.3081   $117.31   $117.30   $117.30  
  Purchase #4 $109.92   7.105%   $117.7298   $117.73   $117.75   $117.70  
  Purchase #5 $206.35   11.790%   $230.6787   $230.68   $230.70   $230.70  
  Purchase #6 $111.88   12.612%   $125.9903   $125.99   $126.00   $126.00  
  Purchase #7 $245.92   9.271%   $268.7192   $268.72   $268.70   $268.70  
  7 purchase totals = $1,051.29       $1,161.4806   $1,161.49   $1,161.50   $1,161.50