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 $95.75   6.792%   $102.2533   $102.25   $102.25   $102.30  
  Purchase #2 $244.87   5.621%   $258.6341   $258.63   $258.65   $258.60  
  Purchase #3 $210.62   6.755%   $224.8474   $224.85   $224.85   $224.80  
  Purchase #4 $205.76   6.758%   $219.6653   $219.67   $219.65   $219.70  
  Purchase #5 $226.50   4.703%   $237.1523   $237.15   $237.15   $237.20  
  Purchase #6 $133.49   10.516%   $147.5278   $147.53   $147.55   $147.50  
  Purchase #7 $239.38   4.779%   $250.82   $250.82   $250.80   $250.80  
  7 purchase totals = $1,356.37       $1,440.9002   $1,440.90   $1,440.90   $1,440.90