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 $60.81   3.263%   $62.7942   $62.79   $62.80   $62.80  
  Purchase #2 $104.63   9.145%   $114.1984   $114.20   $114.20   $114.20  
  Purchase #3 $164.76   6.442%   $175.3738   $175.37   $175.35   $175.40  
  Purchase #4 $186.56   3.711%   $193.4832   $193.48   $193.50   $193.50  
  Purchase #5 $152.42   4.856%   $159.8215   $159.82   $159.80   $159.80  
  Purchase #6 $21.46   11.347%   $23.8951   $23.90   $23.90   $23.90  
  Purchase #7 $224.58   6.573%   $239.3416   $239.34   $239.35   $239.30  
  7 purchase totals = $915.22       $968.9078   $968.90   $968.90   $968.90