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 $61.33   12.149%   $68.781   $68.78   $68.80   $68.80  
  Purchase #2 $197.38   5.763%   $208.755   $208.76   $208.75   $208.80  
  Purchase #3 $202.81   3.867%   $210.6527   $210.65   $210.65   $210.70  
  Purchase #4 $145.46   13.110%   $164.5298   $164.53   $164.55   $164.50  
  Purchase #5 $83.72   3.137%   $86.3463   $86.35   $86.35   $86.30  
  Purchase #6 $248.60   3.691%   $257.7758   $257.78   $257.80   $257.80  
  Purchase #7 $100.74   12.516%   $113.3486   $113.35   $113.35   $113.30  
  7 purchase totals = $1,040.04       $1,110.1892   $1,110.20   $1,110.25   $1,110.20