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 $126.94   7.210%   $136.0924   $136.09   $136.10   $136.10  
  Purchase #2 $136.99   3.549%   $141.8518   $141.85   $141.85   $141.90  
  Purchase #3 $163.50   12.195%   $183.4388   $183.44   $183.45   $183.40  
  Purchase #4 $63.79   4.546%   $66.6899   $66.69   $66.70   $66.70  
  Purchase #5 $199.99   4.750%   $209.4895   $209.49   $209.50   $209.50  
  Purchase #6 $235.55   6.793%   $251.5509   $251.55   $251.55   $251.60  
  Purchase #7 $125.45   3.585%   $129.9474   $129.95   $129.95   $129.90  
  7 purchase totals = $1,052.21       $1,119.0607   $1,119.06   $1,119.10   $1,119.10