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 $216.55   8.807%   $235.6216   $235.62   $235.60   $235.60  
  Purchase #2 $223.70   8.822%   $243.4348   $243.43   $243.45   $243.40  
  Purchase #3 $143.82   11.619%   $160.5304   $160.53   $160.55   $160.50  
  Purchase #4 $13.47   12.477%   $15.1507   $15.15   $15.15   $15.20  
  Purchase #5 $170.55   12.355%   $191.6215   $191.62   $191.60   $191.60  
  Purchase #6 $54.47   6.466%   $57.992   $57.99   $58.00   $58.00  
  Purchase #7 $43.33   8.447%   $46.9901   $46.99   $47.00   $47.00  
  7 purchase totals = $865.89       $951.3411   $951.33   $951.35   $951.30