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 $38.84   10.836%   $43.0487   $43.05   $43.05   $43.00  
  Purchase #2 $250.32   4.546%   $261.6995   $261.70   $261.70   $261.70  
  Purchase #3 $95.41   9.179%   $104.1677   $104.17   $104.15   $104.20  
  Purchase #4 $128.81   10.302%   $142.08   $142.08   $142.10   $142.10  
  Purchase #5 $105.82   4.456%   $110.5353   $110.54   $110.55   $110.50  
  Purchase #6 $230.53   6.249%   $244.9358   $244.94   $244.95   $244.90  
  Purchase #7 $76.35   4.689%   $79.9301   $79.93   $79.95   $79.90  
  7 purchase totals = $926.08       $986.3971   $986.41   $986.45   $986.30