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 $85.88   10.621%   $95.0013   $95.00   $95.00   $95.00  
  Purchase #2 $87.30   4.322%   $91.0731   $91.07   $91.05   $91.10  
  Purchase #3 $233.25   10.248%   $257.1535   $257.15   $257.15   $257.20  
  Purchase #4 $54.89   12.836%   $61.9357   $61.94   $61.95   $61.90  
  Purchase #5 $74.81   12.507%   $84.1665   $84.17   $84.15   $84.20  
  Purchase #6 $248.70   6.710%   $265.3878   $265.39   $265.40   $265.40  
  Purchase #7 $236.64   5.535%   $249.738   $249.74   $249.75   $249.70  
  7 purchase totals = $1,021.47       $1,104.4559   $1,104.46   $1,104.45   $1,104.50