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 $195.41   6.724%   $208.5494   $208.55   $208.55   $208.50  
  Purchase #2 $206.32   11.122%   $229.2669   $229.27   $229.25   $229.30  
  Purchase #3 $153.33   13.873%   $174.6015   $174.60   $174.60   $174.60  
  Purchase #4 $187.61   5.469%   $197.8704   $197.87   $197.85   $197.90  
  Purchase #5 $57.93   6.103%   $61.4655   $61.47   $61.45   $61.50  
  Purchase #6 $33.75   6.740%   $36.0248   $36.02   $36.00   $36.00  
  Purchase #7 $127.81   9.765%   $140.2906   $140.29   $140.30   $140.30  
  7 purchase totals = $962.16       $1,048.0691   $1,048.07   $1,048.00   $1,048.10