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 $24.50   6.368%   $26.0602   $26.06   $26.05   $26.10  
  Purchase #2 $203.62   13.550%   $231.2105   $231.21   $231.20   $231.20  
  Purchase #3 $154.76   9.677%   $169.7361   $169.74   $169.75   $169.70  
  Purchase #4 $174.56   6.303%   $185.5625   $185.56   $185.55   $185.60  
  Purchase #5 $82.47   13.175%   $93.3354   $93.34   $93.35   $93.30  
  Purchase #6 $115.59   3.436%   $119.5617   $119.56   $119.55   $119.60  
  Purchase #7 $80.48   7.841%   $86.7904   $86.79   $86.80   $86.80  
  7 purchase totals = $835.98       $912.2568   $912.26   $912.25   $912.30