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 $182.62   6.579%   $194.6346   $194.63   $194.65   $194.60  
  Purchase #2 $241.39   5.280%   $254.1354   $254.14   $254.15   $254.10  
  Purchase #3 $155.54   10.126%   $171.29   $171.29   $171.30   $171.30  
  Purchase #4 $188.82   3.743%   $195.8875   $195.89   $195.90   $195.90  
  Purchase #5 $248.49   7.109%   $266.1552   $266.16   $266.15   $266.20  
  Purchase #6 $32.82   7.104%   $35.1515   $35.15   $35.15   $35.20  
  Purchase #7 $192.49   8.341%   $208.5456   $208.55   $208.55   $208.50  
  7 purchase totals = $1,242.17       $1,325.7998   $1,325.81   $1,325.85   $1,325.80