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 $60.82   3.539%   $62.9724   $62.97   $62.95   $63.00  
  Purchase #2 $214.75   7.761%   $231.4167   $231.42   $231.40   $231.40  
  Purchase #3 $26.28   7.159%   $28.1614   $28.16   $28.15   $28.20  
  Purchase #4 $141.40   13.461%   $160.4339   $160.43   $160.45   $160.40  
  Purchase #5 $54.64   4.722%   $57.2201   $57.22   $57.20   $57.20  
  Purchase #6 $58.74   7.819%   $63.3329   $63.33   $63.35   $63.30  
  Purchase #7 $104.54   9.255%   $114.2152   $114.22   $114.20   $114.20  
  7 purchase totals = $661.17       $717.7526   $717.75   $717.70   $717.70