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 $174.66   13.164%   $197.6522   $197.65   $197.65   $197.70  
  Purchase #2 $243.78   3.804%   $253.0534   $253.05   $253.05   $253.10  
  Purchase #3 $148.46   7.558%   $159.6806   $159.68   $159.70   $159.70  
  Purchase #4 $167.53   13.477%   $190.108   $190.11   $190.10   $190.10  
  Purchase #5 $18.49   12.235%   $20.7523   $20.75   $20.75   $20.80  
  Purchase #6 $23.40   12.430%   $26.3086   $26.31   $26.30   $26.30  
  Purchase #7 $72.36   6.564%   $77.1097   $77.11   $77.10   $77.10  
  7 purchase totals = $848.68       $924.6648   $924.66   $924.65   $924.80