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 $211.54   12.298%   $237.5552   $237.56   $237.55   $237.60  
  Purchase #2 $195.82   3.504%   $202.6815   $202.68   $202.70   $202.70  
  Purchase #3 $16.28   11.102%   $18.0874   $18.09   $18.10   $18.10  
  Purchase #4 $163.69   5.400%   $172.5293   $172.53   $172.55   $172.50  
  Purchase #5 $167.85   13.473%   $190.4644   $190.46   $190.45   $190.50  
  Purchase #6 $188.57   4.703%   $197.4384   $197.44   $197.45   $197.40  
  Purchase #7 $71.92   4.385%   $75.0737   $75.07   $75.05   $75.10  
  7 purchase totals = $1,015.67       $1,093.8299   $1,093.83   $1,093.85   $1,093.90