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 $91.95   4.346%   $95.9461   $95.95   $95.95   $95.90  
  Purchase #2 $51.63   13.330%   $58.5123   $58.51   $58.50   $58.50  
  Purchase #3 $191.26   5.835%   $202.42   $202.42   $202.40   $202.40  
  Purchase #4 $164.84   10.830%   $182.6922   $182.69   $182.70   $182.70  
  Purchase #5 $107.51   4.292%   $112.1243   $112.12   $112.10   $112.10  
  Purchase #6 $133.48   13.770%   $151.8602   $151.86   $151.85   $151.90  
  Purchase #7 $32.61   8.557%   $35.4004   $35.40   $35.40   $35.40  
  7 purchase totals = $773.28       $838.9555   $838.95   $838.90   $838.90