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 $36.75   12.281%   $41.2633   $41.26   $41.25   $41.30  
  Purchase #2 $201.61   3.593%   $208.8538   $208.85   $208.85   $208.90  
  Purchase #3 $105.63   3.128%   $108.9341   $108.93   $108.95   $108.90  
  Purchase #4 $177.99   12.387%   $200.0376   $200.04   $200.05   $200.00  
  Purchase #5 $94.64   7.316%   $101.5639   $101.56   $101.55   $101.60  
  Purchase #6 $23.98   8.416%   $25.9982   $26.00   $26.00   $26.00  
  Purchase #7 $248.57   3.753%   $257.8988   $257.90   $257.90   $257.90  
  7 purchase totals = $889.17       $944.5497   $944.54   $944.55   $944.60