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 $97.26   7.611%   $104.6625   $104.66   $104.65   $104.70  
  Purchase #2 $228.26   4.109%   $237.6392   $237.64   $237.65   $237.60  
  Purchase #3 $111.96   11.583%   $124.9283   $124.93   $124.95   $124.90  
  Purchase #4 $132.56   12.301%   $148.8662   $148.87   $148.85   $148.90  
  Purchase #5 $79.60   3.147%   $82.105   $82.11   $82.10   $82.10  
  Purchase #6 $158.97   11.167%   $176.7222   $176.72   $176.70   $176.70  
  Purchase #7 $74.65   7.770%   $80.4503   $80.45   $80.45   $80.50  
  7 purchase totals = $883.26       $955.3737   $955.38   $955.35   $955.40