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 $118.70   13.607%   $134.8515   $134.85   $134.85   $134.90  
  Purchase #2 $231.74   12.626%   $260.9995   $261.00   $261.00   $261.00  
  Purchase #3 $44.80   6.869%   $47.8773   $47.88   $47.90   $47.90  
  Purchase #4 $217.73   10.168%   $239.8688   $239.87   $239.85   $239.90  
  Purchase #5 $239.64   10.688%   $265.2527   $265.25   $265.25   $265.30  
  Purchase #6 $39.52   5.499%   $41.6932   $41.69   $41.70   $41.70  
  Purchase #7 $153.87   11.735%   $171.9266   $171.93   $171.95   $171.90  
  7 purchase totals = $1,046.00       $1,162.4696   $1,162.47   $1,162.50   $1,162.60