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 $171.86   13.804%   $195.5836   $195.58   $195.60   $195.60  
  Purchase #2 $53.67   7.391%   $57.6367   $57.64   $57.65   $57.60  
  Purchase #3 $41.98   8.169%   $45.4093   $45.41   $45.40   $45.40  
  Purchase #4 $98.46   5.856%   $104.2258   $104.23   $104.25   $104.20  
  Purchase #5 $179.90   8.522%   $195.2311   $195.23   $195.25   $195.20  
  Purchase #6 $49.69   3.649%   $51.5032   $51.50   $51.50   $51.50  
  Purchase #7 $231.31   6.590%   $246.5533   $246.55   $246.55   $246.60  
  7 purchase totals = $826.87       $896.1430   $896.14   $896.20   $896.10