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 $62.25   11.774%   $69.5793   $69.58   $69.60   $69.60  
  Purchase #2 $76.51   9.238%   $83.578   $83.58   $83.60   $83.60  
  Purchase #3 $130.91   6.535%   $139.465   $139.47   $139.45   $139.50  
  Purchase #4 $56.45   9.725%   $61.9398   $61.94   $61.95   $61.90  
  Purchase #5 $199.68   9.326%   $218.3022   $218.30   $218.30   $218.30  
  Purchase #6 $229.31   4.781%   $240.2733   $240.27   $240.25   $240.30  
  Purchase #7 $239.96   3.239%   $247.7323   $247.73   $247.75   $247.70  
  7 purchase totals = $995.07       $1,060.8699   $1,060.87   $1,060.90   $1,060.90