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 $96.96   4.607%   $101.4269   $101.43   $101.45   $101.40  
  Purchase #2 $165.53   12.755%   $186.6434   $186.64   $186.65   $186.60  
  Purchase #3 $247.53   10.345%   $273.137   $273.14   $273.15   $273.10  
  Purchase #4 $112.66   12.106%   $126.2986   $126.30   $126.30   $126.30  
  Purchase #5 $95.25   3.542%   $98.6238   $98.62   $98.60   $98.60  
  Purchase #6 $86.74   4.487%   $90.632   $90.63   $90.65   $90.60  
  Purchase #7 $124.76   8.152%   $134.9304   $134.93   $134.95   $134.90  
  7 purchase totals = $929.43       $1,011.6921   $1,011.69   $1,011.75   $1,011.50