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 $31.98   12.366%   $35.9346   $35.93   $35.95   $35.90  
  Purchase #2 $126.56   4.662%   $132.4602   $132.46   $132.45   $132.50  
  Purchase #3 $167.30   3.781%   $173.6256   $173.63   $173.65   $173.60  
  Purchase #4 $241.45   6.725%   $257.6875   $257.69   $257.70   $257.70  
  Purchase #5 $158.76   11.431%   $176.9079   $176.91   $176.90   $176.90  
  Purchase #6 $230.79   3.864%   $239.7077   $239.71   $239.70   $239.70  
  Purchase #7 $206.51   13.137%   $233.6392   $233.64   $233.65   $233.60  
  7 purchase totals = $1,163.35       $1,249.9627   $1,249.97   $1,250.00   $1,249.90