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 $179.61   8.711%   $195.2558   $195.26   $195.25   $195.30  
  Purchase #2 $61.55   13.675%   $69.967   $69.97   $69.95   $70.00  
  Purchase #3 $39.49   5.576%   $41.692   $41.69   $41.70   $41.70  
  Purchase #4 $46.99   9.294%   $51.3573   $51.36   $51.35   $51.40  
  Purchase #5 $197.62   5.338%   $208.169   $208.17   $208.15   $208.20  
  Purchase #6 $42.38   10.840%   $46.974   $46.97   $46.95   $47.00  
  Purchase #7 $174.55   4.511%   $182.424   $182.42   $182.40   $182.40  
  7 purchase totals = $742.19       $795.8391   $795.84   $795.75   $796.00