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 $127.73   13.263%   $144.6708   $144.67   $144.65   $144.70  
  Purchase #2 $166.79   4.360%   $174.062   $174.06   $174.05   $174.10  
  Purchase #3 $208.56   3.435%   $215.724   $215.72   $215.70   $215.70  
  Purchase #4 $82.76   12.806%   $93.3582   $93.36   $93.35   $93.40  
  Purchase #5 $6.54   5.749%   $6.916   $6.92   $6.90   $6.90  
  Purchase #6 $179.26   8.307%   $194.1511   $194.15   $194.15   $194.20  
  Purchase #7 $124.94   7.231%   $133.9744   $133.97   $133.95   $134.00  
  7 purchase totals = $896.58       $962.8565   $962.85   $962.75   $963.00