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 $215.25   11.405%   $239.7993   $239.80   $239.80   $239.80  
  Purchase #2 $60.94   4.287%   $63.5525   $63.55   $63.55   $63.60  
  Purchase #3 $208.88   7.179%   $223.8755   $223.88   $223.90   $223.90  
  Purchase #4 $232.63   6.252%   $247.174   $247.17   $247.15   $247.20  
  Purchase #5 $165.40   6.755%   $176.5728   $176.57   $176.55   $176.60  
  Purchase #6 $136.47   6.661%   $145.5603   $145.56   $145.55   $145.60  
  Purchase #7 $93.75   11.668%   $104.6888   $104.69   $104.70   $104.70  
  7 purchase totals = $1,113.32       $1,201.2232   $1,201.22   $1,201.20   $1,201.40