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 $103.28   10.762%   $114.395   $114.40   $114.40   $114.40  
  Purchase #2 $207.35   13.270%   $234.8653   $234.87   $234.85   $234.90  
  Purchase #3 $195.76   12.381%   $219.997   $220.00   $220.00   $220.00  
  Purchase #4 $22.88   3.249%   $23.6234   $23.62   $23.60   $23.60  
  Purchase #5 $162.92   6.740%   $173.9008   $173.90   $173.90   $173.90  
  Purchase #6 $185.79   5.823%   $196.6086   $196.61   $196.60   $196.60  
  Purchase #7 $19.87   13.689%   $22.59   $22.59   $22.60   $22.60  
  7 purchase totals = $897.85       $985.9801   $985.99   $985.95   $986.00