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 $62.90   9.790%   $69.0579   $69.06   $69.05   $69.10  
  Purchase #2 $38.66   12.417%   $43.4604   $43.46   $43.45   $43.50  
  Purchase #3 $223.86   9.149%   $244.341   $244.34   $244.35   $244.30  
  Purchase #4 $218.44   8.722%   $237.4923   $237.49   $237.50   $237.50  
  Purchase #5 $151.83   10.710%   $168.091   $168.09   $168.10   $168.10  
  Purchase #6 $39.52   12.863%   $44.6035   $44.60   $44.60   $44.60  
  Purchase #7 $210.57   7.553%   $226.4744   $226.47   $226.45   $226.50  
  7 purchase totals = $945.78       $1,033.5205   $1,033.51   $1,033.50   $1,033.60