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 $177.32   10.402%   $195.7648   $195.76   $195.75   $195.80  
  Purchase #2 $176.29   12.641%   $198.5748   $198.57   $198.55   $198.60  
  Purchase #3 $122.34   6.591%   $130.4034   $130.40   $130.40   $130.40  
  Purchase #4 $63.71   4.465%   $66.5547   $66.55   $66.55   $66.60  
  Purchase #5 $247.83   9.396%   $271.1161   $271.12   $271.10   $271.10  
  Purchase #6 $244.25   7.792%   $263.282   $263.28   $263.30   $263.30  
  Purchase #7 $80.67   3.457%   $83.4588   $83.46   $83.45   $83.50  
  7 purchase totals = $1,112.41       $1,209.1546   $1,209.14   $1,209.10   $1,209.30