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 $195.83   6.476%   $208.512   $208.51   $208.50   $208.50  
  Purchase #2 $56.44   9.102%   $61.5772   $61.58   $61.60   $61.60  
  Purchase #3 $48.27   5.863%   $51.1001   $51.10   $51.10   $51.10  
  Purchase #4 $150.27   8.507%   $163.0535   $163.05   $163.05   $163.10  
  Purchase #5 $186.92   8.664%   $203.1147   $203.11   $203.10   $203.10  
  Purchase #6 $114.41   3.491%   $118.4041   $118.40   $118.40   $118.40  
  Purchase #7 $242.55   13.668%   $275.7017   $275.70   $275.70   $275.70  
  7 purchase totals = $994.69       $1,081.4633   $1,081.45   $1,081.45   $1,081.50