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 $176.92   13.358%   $200.553   $200.55   $200.55   $200.60  
  Purchase #2 $174.76   13.478%   $198.3142   $198.31   $198.30   $198.30  
  Purchase #3 $173.47   3.510%   $179.5588   $179.56   $179.55   $179.60  
  Purchase #4 $33.80   8.574%   $36.698   $36.70   $36.70   $36.70  
  Purchase #5 $155.59   6.477%   $165.6676   $165.67   $165.65   $165.70  
  Purchase #6 $62.68   9.282%   $68.498   $68.50   $68.50   $68.50  
  Purchase #7 $74.82   9.541%   $81.9586   $81.96   $81.95   $82.00  
  7 purchase totals = $852.04       $931.2482   $931.25   $931.20   $931.40