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 $74.58   3.187%   $76.9569   $76.96   $76.95   $77.00  
  Purchase #2 $248.81   10.790%   $275.6566   $275.66   $275.65   $275.70  
  Purchase #3 $103.55   7.587%   $111.4063   $111.41   $111.40   $111.40  
  Purchase #4 $121.54   8.566%   $131.9511   $131.95   $131.95   $132.00  
  Purchase #5 $197.92   13.594%   $224.8252   $224.83   $224.85   $224.80  
  Purchase #6 $123.43   9.414%   $135.0497   $135.05   $135.05   $135.00  
  Purchase #7 $195.33   13.135%   $220.9866   $220.99   $221.00   $221.00  
  7 purchase totals = $1,065.16       $1,176.8324   $1,176.85   $1,176.85   $1,176.90