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 $103.44   10.198%   $113.9888   $113.99   $114.00   $114.00  
  Purchase #2 $201.98   8.190%   $218.5222   $218.52   $218.50   $218.50  
  Purchase #3 $125.84   3.769%   $130.5829   $130.58   $130.60   $130.60  
  Purchase #4 $203.42   6.394%   $216.4267   $216.43   $216.45   $216.40  
  Purchase #5 $29.69   13.548%   $33.7124   $33.71   $33.70   $33.70  
  Purchase #6 $248.93   5.188%   $261.8445   $261.84   $261.85   $261.80  
  Purchase #7 $58.89   3.530%   $60.9688   $60.97   $60.95   $61.00  
  7 purchase totals = $972.19       $1,036.0463   $1,036.04   $1,036.05   $1,036.00