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 $182.29   5.693%   $192.6678   $192.67   $192.65   $192.70  
  Purchase #2 $198.36   8.856%   $215.9268   $215.93   $215.95   $215.90  
  Purchase #3 $17.50   5.221%   $18.4137   $18.41   $18.40   $18.40  
  Purchase #4 $56.31   10.491%   $62.2175   $62.22   $62.20   $62.20  
  Purchase #5 $213.69   8.796%   $232.4862   $232.49   $232.50   $232.50  
  Purchase #6 $138.99   9.307%   $151.9258   $151.93   $151.95   $151.90  
  Purchase #7 $80.94   3.297%   $83.6086   $83.61   $83.60   $83.60  
  7 purchase totals = $888.08       $957.2464   $957.26   $957.25   $957.20