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 $112.57   5.762%   $119.0563   $119.06   $119.05   $119.10  
  Purchase #2 $224.39   4.841%   $235.2527   $235.25   $235.25   $235.30  
  Purchase #3 $126.36   6.714%   $134.8438   $134.84   $134.85   $134.80  
  Purchase #4 $58.40   8.731%   $63.4989   $63.50   $63.50   $63.50  
  Purchase #5 $164.44   4.246%   $171.4221   $171.42   $171.40   $171.40  
  Purchase #6 $66.52   7.595%   $71.5722   $71.57   $71.55   $71.60  
  Purchase #7 $160.80   4.413%   $167.8961   $167.90   $167.90   $167.90  
  7 purchase totals = $913.48       $963.5421   $963.54   $963.50   $963.60