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 $63.59   9.439%   $69.5923   $69.59   $69.60   $69.60  
  Purchase #2 $112.42   12.526%   $126.5017   $126.50   $126.50   $126.50  
  Purchase #3 $210.92   9.561%   $231.0861   $231.09   $231.10   $231.10  
  Purchase #4 $112.61   8.297%   $121.9533   $121.95   $121.95   $122.00  
  Purchase #5 $237.25   11.572%   $264.7046   $264.70   $264.70   $264.70  
  Purchase #6 $170.33   9.433%   $186.3972   $186.40   $186.40   $186.40  
  Purchase #7 $63.44   6.790%   $67.7476   $67.75   $67.75   $67.70  
  7 purchase totals = $970.56       $1,067.9828   $1,067.98   $1,068.00   $1,068.00