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 $59.51   4.255%   $62.0422   $62.04   $62.05   $62.00  
  Purchase #2 $39.86   9.404%   $43.6084   $43.61   $43.60   $43.60  
  Purchase #3 $188.37   7.254%   $202.0344   $202.03   $202.05   $202.00  
  Purchase #4 $15.51   13.530%   $17.6085   $17.61   $17.60   $17.60  
  Purchase #5 $204.73   13.804%   $232.9909   $232.99   $233.00   $233.00  
  Purchase #6 $67.92   4.262%   $70.8148   $70.81   $70.80   $70.80  
  Purchase #7 $134.26   6.845%   $143.4501   $143.45   $143.45   $143.50  
  7 purchase totals = $710.16       $772.5493   $772.54   $772.55   $772.50