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 $69.53   10.467%   $76.8077   $76.81   $76.80   $76.80  
  Purchase #2 $234.34   13.332%   $265.5822   $265.58   $265.60   $265.60  
  Purchase #3 $242.42   13.677%   $275.5758   $275.58   $275.60   $275.60  
  Purchase #4 $105.83   9.102%   $115.4626   $115.46   $115.45   $115.50  
  Purchase #5 $174.27   11.798%   $194.8304   $194.83   $194.85   $194.80  
  Purchase #6 $74.36   3.508%   $76.9685   $76.97   $76.95   $77.00  
  Purchase #7 $26.60   4.221%   $27.7228   $27.72   $27.70   $27.70  
  7 purchase totals = $927.35       $1,032.9500   $1,032.95   $1,032.95   $1,033.00