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 $118.69   6.159%   $126.0001   $126.00   $126.00   $126.00  
  Purchase #2 $91.50   13.436%   $103.7939   $103.79   $103.80   $103.80  
  Purchase #3 $237.89   11.396%   $264.9999   $265.00   $265.00   $265.00  
  Purchase #4 $69.54   12.536%   $78.2575   $78.26   $78.25   $78.30  
  Purchase #5 $86.51   11.693%   $96.6256   $96.63   $96.65   $96.60  
  Purchase #6 $92.57   8.643%   $100.5708   $100.57   $100.55   $100.60  
  Purchase #7 $204.36   5.812%   $216.2374   $216.24   $216.25   $216.20  
  7 purchase totals = $901.06       $986.4852   $986.49   $986.50   $986.50