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 $43.64   5.458%   $46.0219   $46.02   $46.00   $46.00  
  Purchase #2 $234.69   11.135%   $260.8227   $260.82   $260.80   $260.80  
  Purchase #3 $98.43   8.755%   $107.0475   $107.05   $107.05   $107.00  
  Purchase #4 $203.55   4.835%   $213.3916   $213.39   $213.40   $213.40  
  Purchase #5 $23.45   5.225%   $24.6753   $24.68   $24.70   $24.70  
  Purchase #6 $161.74   13.243%   $183.1592   $183.16   $183.15   $183.20  
  Purchase #7 $132.81   6.826%   $141.8756   $141.88   $141.90   $141.90  
  7 purchase totals = $898.31       $976.9938   $977.00   $977.00   $977.00