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 $177.42   11.372%   $197.5962   $197.60   $197.60   $197.60  
  Purchase #2 $228.67   5.778%   $241.8826   $241.88   $241.90   $241.90  
  Purchase #3 $56.75   5.312%   $59.7646   $59.76   $59.75   $59.80  
  Purchase #4 $232.72   12.291%   $261.3236   $261.32   $261.30   $261.30  
  Purchase #5 $30.29   11.548%   $33.7879   $33.79   $33.80   $33.80  
  Purchase #6 $44.97   10.517%   $49.6995   $49.70   $49.70   $49.70  
  Purchase #7 $94.64   10.784%   $104.846   $104.85   $104.85   $104.80  
  7 purchase totals = $865.46       $948.9004   $948.90   $948.90   $948.90