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 $56.61   3.134%   $58.3842   $58.38   $58.40   $58.40  
  Purchase #2 $199.56   5.300%   $210.1367   $210.14   $210.15   $210.10  
  Purchase #3 $200.25   5.593%   $211.45   $211.45   $211.45   $211.50  
  Purchase #4 $85.74   7.193%   $91.9073   $91.91   $91.90   $91.90  
  Purchase #5 $219.68   3.324%   $226.9822   $226.98   $227.00   $227.00  
  Purchase #6 $74.77   8.391%   $81.044   $81.04   $81.05   $81.00  
  Purchase #7 $231.56   6.661%   $246.9842   $246.98   $247.00   $247.00  
  7 purchase totals = $1,068.17       $1,126.8886   $1,126.88   $1,126.95   $1,126.90