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 $54.38   13.871%   $61.923   $61.92   $61.90   $61.90  
  Purchase #2 $30.49   12.820%   $34.3988   $34.40   $34.40   $34.40  
  Purchase #3 $79.58   5.433%   $83.9036   $83.90   $83.90   $83.90  
  Purchase #4 $201.75   8.125%   $218.1422   $218.14   $218.15   $218.10  
  Purchase #5 $66.66   5.372%   $70.241   $70.24   $70.25   $70.20  
  Purchase #6 $114.99   3.164%   $118.6283   $118.63   $118.65   $118.60  
  Purchase #7 $165.57   6.807%   $176.8403   $176.84   $176.85   $176.80  
  7 purchase totals = $713.42       $764.0772   $764.07   $764.10   $763.90