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 $163.77   11.786%   $183.0719   $183.07   $183.05   $183.10  
  Purchase #2 $198.65   8.540%   $215.6147   $215.61   $215.60   $215.60  
  Purchase #3 $108.64   8.715%   $118.108   $118.11   $118.10   $118.10  
  Purchase #4 $50.83   4.158%   $52.9435   $52.94   $52.95   $52.90  
  Purchase #5 $185.93   8.218%   $201.2097   $201.21   $201.20   $201.20  
  Purchase #6 $209.49   8.187%   $226.6409   $226.64   $226.65   $226.60  
  Purchase #7 $101.25   4.717%   $106.026   $106.03   $106.05   $106.00  
  7 purchase totals = $1,018.56       $1,103.6147   $1,103.61   $1,103.60   $1,103.50