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 $86.41   9.126%   $94.2958   $94.30   $94.30   $94.30  
  Purchase #2 $53.33   12.553%   $60.0245   $60.02   $60.00   $60.00  
  Purchase #3 $173.30   3.339%   $179.0865   $179.09   $179.10   $179.10  
  Purchase #4 $248.77   9.269%   $271.8285   $271.83   $271.85   $271.80  
  Purchase #5 $96.62   6.594%   $102.9911   $102.99   $103.00   $103.00  
  Purchase #6 $236.55   6.599%   $252.1599   $252.16   $252.15   $252.20  
  Purchase #7 $246.39   3.779%   $255.7011   $255.70   $255.70   $255.70  
  7 purchase totals = $1,141.37       $1,216.0874   $1,216.09   $1,216.10   $1,216.10