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 $23.50   10.825%   $26.0439   $26.04   $26.05   $26.00  
  Purchase #2 $44.35   4.166%   $46.1976   $46.20   $46.20   $46.20  
  Purchase #3 $196.81   5.500%   $207.6346   $207.63   $207.65   $207.60  
  Purchase #4 $101.57   13.292%   $115.0707   $115.07   $115.05   $115.10  
  Purchase #5 $80.66   6.276%   $85.7222   $85.72   $85.70   $85.70  
  Purchase #6 $154.60   10.805%   $171.3045   $171.30   $171.30   $171.30  
  Purchase #7 $169.84   12.309%   $190.7456   $190.75   $190.75   $190.70  
  7 purchase totals = $771.33       $842.7191   $842.71   $842.70   $842.60