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 $103.41   10.861%   $114.6414   $114.64   $114.65   $114.60  
  Purchase #2 $113.54   3.113%   $117.0745   $117.07   $117.05   $117.10  
  Purchase #3 $160.63   13.430%   $182.2026   $182.20   $182.20   $182.20  
  Purchase #4 $65.89   13.658%   $74.8893   $74.89   $74.90   $74.90  
  Purchase #5 $201.63   6.123%   $213.9758   $213.98   $214.00   $214.00  
  Purchase #6 $177.37   9.131%   $193.5657   $193.57   $193.55   $193.60  
  Purchase #7 $52.42   9.208%   $57.2468   $57.25   $57.25   $57.20  
  7 purchase totals = $874.89       $953.5961   $953.60   $953.60   $953.60