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 $208.76   7.756%   $224.9514   $224.95   $224.95   $225.00  
  Purchase #2 $58.87   3.556%   $60.9634   $60.96   $60.95   $61.00  
  Purchase #3 $86.90   9.735%   $95.3597   $95.36   $95.35   $95.40  
  Purchase #4 $176.39   10.649%   $195.1738   $195.17   $195.15   $195.20  
  Purchase #5 $39.48   6.679%   $42.1169   $42.12   $42.10   $42.10  
  Purchase #6 $209.38   4.358%   $218.5048   $218.50   $218.50   $218.50  
  Purchase #7 $149.77   12.347%   $168.2621   $168.26   $168.25   $168.30  
  7 purchase totals = $929.55       $1,005.3321   $1,005.32   $1,005.25   $1,005.50