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 $101.82   12.561%   $114.6096   $114.61   $114.60   $114.60  
  Purchase #2 $114.25   7.395%   $122.6988   $122.70   $122.70   $122.70  
  Purchase #3 $228.77   8.688%   $248.6455   $248.65   $248.65   $248.60  
  Purchase #4 $92.92   9.202%   $101.4705   $101.47   $101.45   $101.50  
  Purchase #5 $226.83   11.541%   $253.0085   $253.01   $253.00   $253.00  
  Purchase #6 $215.34   7.236%   $230.922   $230.92   $230.90   $230.90  
  Purchase #7 $169.28   10.442%   $186.9562   $186.96   $186.95   $187.00  
  7 purchase totals = $1,149.21       $1,258.3111   $1,258.32   $1,258.25   $1,258.30