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 $23.44   10.832%   $25.979   $25.98   $26.00   $26.00  
  Purchase #2 $178.85   6.227%   $189.987   $189.99   $190.00   $190.00  
  Purchase #3 $193.46   7.797%   $208.5441   $208.54   $208.55   $208.50  
  Purchase #4 $126.96   5.597%   $134.066   $134.07   $134.05   $134.10  
  Purchase #5 $86.35   6.803%   $92.2244   $92.22   $92.20   $92.20  
  Purchase #6 $239.83   10.826%   $265.794   $265.79   $265.80   $265.80  
  Purchase #7 $24.70   6.526%   $26.3119   $26.31   $26.30   $26.30  
  7 purchase totals = $873.59       $942.9064   $942.90   $942.90   $942.90