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 $69.25   10.528%   $76.5406   $76.54   $76.55   $76.50  
  Purchase #2 $210.62   11.793%   $235.4584   $235.46   $235.45   $235.50  
  Purchase #3 $90.92   11.811%   $101.6586   $101.66   $101.65   $101.70  
  Purchase #4 $250.84   7.326%   $269.2165   $269.22   $269.20   $269.20  
  Purchase #5 $233.80   10.608%   $258.6015   $258.60   $258.60   $258.60  
  Purchase #6 $230.96   7.262%   $247.7323   $247.73   $247.75   $247.70  
  Purchase #7 $133.27   4.832%   $139.7096   $139.71   $139.70   $139.70  
  7 purchase totals = $1,219.66       $1,328.9175   $1,328.92   $1,328.90   $1,328.90