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 $107.48   10.672%   $118.9503   $118.95   $118.95   $119.00  
  Purchase #2 $140.68   8.724%   $152.9529   $152.95   $152.95   $153.00  
  Purchase #3 $10.66   13.566%   $12.1061   $12.11   $12.10   $12.10  
  Purchase #4 $193.70   7.642%   $208.5026   $208.50   $208.50   $208.50  
  Purchase #5 $54.48   8.769%   $59.2574   $59.26   $59.25   $59.30  
  Purchase #6 $152.67   12.604%   $171.9125   $171.91   $171.90   $171.90  
  Purchase #7 $158.42   6.284%   $168.3751   $168.38   $168.40   $168.40  
  7 purchase totals = $818.09       $892.0569   $892.06   $892.05   $892.20