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 $241.93   8.322%   $262.0634   $262.06   $262.05   $262.10  
  Purchase #2 $77.47   8.713%   $84.22   $84.22   $84.20   $84.20  
  Purchase #3 $38.28   7.491%   $41.1476   $41.15   $41.15   $41.10  
  Purchase #4 $122.92   12.797%   $138.6501   $138.65   $138.65   $138.70  
  Purchase #5 $173.85   6.181%   $184.5957   $184.60   $184.60   $184.60  
  Purchase #6 $222.75   8.134%   $240.8685   $240.87   $240.85   $240.90  
  Purchase #7 $146.32   10.301%   $161.3924   $161.39   $161.40   $161.40  
  7 purchase totals = $1,023.52       $1,112.9377   $1,112.94   $1,112.90   $1,113.00