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 $86.99   7.247%   $93.2942   $93.29   $93.30   $93.30  
  Purchase #2 $114.56   9.341%   $125.261   $125.26   $125.25   $125.30  
  Purchase #3 $228.60   7.554%   $245.8684   $245.87   $245.85   $245.90  
  Purchase #4 $206.76   7.343%   $221.9424   $221.94   $221.95   $221.90  
  Purchase #5 $234.56   11.506%   $261.5485   $261.55   $261.55   $261.50  
  Purchase #6 $223.80   5.614%   $236.3641   $236.36   $236.35   $236.40  
  Purchase #7 $205.38   4.581%   $214.7885   $214.79   $214.80   $214.80  
  7 purchase totals = $1,300.65       $1,399.0671   $1,399.06   $1,399.05   $1,399.10