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 $176.47   11.123%   $196.0988   $196.10   $196.10   $196.10  
  Purchase #2 $135.30   10.744%   $149.8366   $149.84   $149.85   $149.80  
  Purchase #3 $53.58   9.538%   $58.6905   $58.69   $58.70   $58.70  
  Purchase #4 $78.56   10.629%   $86.9101   $86.91   $86.90   $86.90  
  Purchase #5 $64.40   8.508%   $69.8792   $69.88   $69.90   $69.90  
  Purchase #6 $248.51   4.231%   $259.0245   $259.02   $259.00   $259.00  
  Purchase #7 $249.27   11.312%   $277.4674   $277.47   $277.45   $277.50  
  7 purchase totals = $1,006.09       $1,097.9071   $1,097.91   $1,097.90   $1,097.90