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 $57.70   5.722%   $61.0016   $61.00   $61.00   $61.00  
  Purchase #2 $243.33   6.218%   $258.4603   $258.46   $258.45   $258.50  
  Purchase #3 $61.47   3.147%   $63.4045   $63.40   $63.40   $63.40  
  Purchase #4 $166.93   5.702%   $176.4483   $176.45   $176.45   $176.40  
  Purchase #5 $146.85   6.266%   $156.0516   $156.05   $156.05   $156.10  
  Purchase #6 $136.62   8.394%   $148.0879   $148.09   $148.10   $148.10  
  Purchase #7 $92.43   7.679%   $99.5277   $99.53   $99.55   $99.50  
  7 purchase totals = $905.33       $962.9819   $962.98   $963.00   $963.00