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 $208.73   13.838%   $237.6141   $237.61   $237.60   $237.60  
  Purchase #2 $13.82   3.380%   $14.2871   $14.29   $14.30   $14.30  
  Purchase #3 $65.63   11.348%   $73.0777   $73.08   $73.10   $73.10  
  Purchase #4 $19.75   5.578%   $20.8517   $20.85   $20.85   $20.90  
  Purchase #5 $76.63   11.596%   $85.516   $85.52   $85.50   $85.50  
  Purchase #6 $90.93   5.460%   $95.8948   $95.89   $95.90   $95.90  
  Purchase #7 $143.88   13.808%   $163.747   $163.75   $163.75   $163.70  
  7 purchase totals = $619.37       $690.9884   $690.99   $691.00   $691.00