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 $173.52   11.657%   $193.7472   $193.75   $193.75   $193.70  
  Purchase #2 $58.70   11.138%   $65.238   $65.24   $65.25   $65.20  
  Purchase #3 $44.80   8.273%   $48.5063   $48.51   $48.50   $48.50  
  Purchase #4 $191.52   3.178%   $197.6065   $197.61   $197.60   $197.60  
  Purchase #5 $44.79   8.335%   $48.5232   $48.52   $48.50   $48.50  
  Purchase #6 $203.83   12.567%   $229.4453   $229.45   $229.45   $229.40  
  Purchase #7 $250.51   4.473%   $261.7153   $261.72   $261.70   $261.70  
  7 purchase totals = $967.67       $1,044.7818   $1,044.80   $1,044.75   $1,044.60