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 $239.87   9.353%   $262.305   $262.31   $262.30   $262.30  
  Purchase #2 $77.73   8.637%   $84.4435   $84.44   $84.45   $84.40  
  Purchase #3 $7.47   9.334%   $8.1672   $8.17   $8.15   $8.20  
  Purchase #4 $220.94   5.768%   $233.6838   $233.68   $233.70   $233.70  
  Purchase #5 $90.28   4.528%   $94.3679   $94.37   $94.35   $94.40  
  Purchase #6 $171.95   11.771%   $192.1902   $192.19   $192.20   $192.20  
  Purchase #7 $173.34   9.303%   $189.4658   $189.47   $189.45   $189.50  
  7 purchase totals = $981.58       $1,064.6234   $1,064.63   $1,064.60   $1,064.70