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 $24.65   5.735%   $26.0637   $26.06   $26.05   $26.10  
  Purchase #2 $134.39   10.535%   $148.548   $148.55   $148.55   $148.50  
  Purchase #3 $127.68   7.223%   $136.9023   $136.90   $136.90   $136.90  
  Purchase #4 $184.32   6.299%   $195.9303   $195.93   $195.95   $195.90  
  Purchase #5 $97.84   6.805%   $104.498   $104.50   $104.50   $104.50  
  Purchase #6 $65.25   10.205%   $71.9088   $71.91   $71.90   $71.90  
  Purchase #7 $86.81   4.598%   $90.8015   $90.80   $90.80   $90.80  
  7 purchase totals = $720.94       $774.6526   $774.65   $774.65   $774.60