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 $86.90   9.598%   $95.2407   $95.24   $95.25   $95.20  
  Purchase #2 $232.86   4.669%   $243.7322   $243.73   $243.75   $243.70  
  Purchase #3 $247.94   5.641%   $261.9263   $261.93   $261.95   $261.90  
  Purchase #4 $51.44   12.515%   $57.8777   $57.88   $57.90   $57.90  
  Purchase #5 $245.59   7.694%   $264.4857   $264.49   $264.50   $264.50  
  Purchase #6 $41.59   13.440%   $47.1797   $47.18   $47.20   $47.20  
  Purchase #7 $109.95   4.754%   $115.177   $115.18   $115.20   $115.20  
  7 purchase totals = $1,016.27       $1,085.6193   $1,085.63   $1,085.75   $1,085.60