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 $63.68   9.206%   $69.5424   $69.54   $69.55   $69.50  
  Purchase #2 $76.69   6.242%   $81.477   $81.48   $81.50   $81.50  
  Purchase #3 $53.70   12.328%   $60.3201   $60.32   $60.30   $60.30  
  Purchase #4 $176.33   11.446%   $196.5127   $196.51   $196.50   $196.50  
  Purchase #5 $206.93   13.634%   $235.1428   $235.14   $235.15   $235.10  
  Purchase #6 $205.38   13.582%   $233.2747   $233.27   $233.25   $233.30  
  Purchase #7 $222.88   10.420%   $246.1041   $246.10   $246.10   $246.10  
  7 purchase totals = $1,005.59       $1,122.3738   $1,122.36   $1,122.35   $1,122.30