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 $229.66   13.567%   $260.818   $260.82   $260.80   $260.80  
  Purchase #2 $235.99   12.246%   $264.8893   $264.89   $264.90   $264.90  
  Purchase #3 $65.44   11.780%   $73.1488   $73.15   $73.15   $73.10  
  Purchase #4 $250.60   9.706%   $274.9232   $274.92   $274.90   $274.90  
  Purchase #5 $72.87   5.240%   $76.6884   $76.69   $76.70   $76.70  
  Purchase #6 $208.59   12.193%   $234.0234   $234.02   $234.00   $234.00  
  Purchase #7 $191.52   13.462%   $217.3024   $217.30   $217.30   $217.30  
  7 purchase totals = $1,254.67       $1,401.7935   $1,401.79   $1,401.75   $1,401.70