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 $68.83   3.499%   $71.2384   $71.24   $71.25   $71.20  
  Purchase #2 $141.34   7.370%   $151.7568   $151.76   $151.75   $151.80  
  Purchase #3 $82.64   4.326%   $86.215   $86.22   $86.20   $86.20  
  Purchase #4 $6.54   6.267%   $6.9499   $6.95   $6.95   $6.90  
  Purchase #5 $68.38   6.126%   $72.569   $72.57   $72.55   $72.60  
  Purchase #6 $103.80   10.117%   $114.3014   $114.30   $114.30   $114.30  
  Purchase #7 $240.45   5.664%   $254.0691   $254.07   $254.05   $254.10  
  7 purchase totals = $711.98       $757.0996   $757.11   $757.05   $757.10