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 $41.28   8.223%   $44.6745   $44.67   $44.65   $44.70  
  Purchase #2 $187.47   6.680%   $199.993   $199.99   $200.00   $200.00  
  Purchase #3 $127.35   12.832%   $143.6916   $143.69   $143.70   $143.70  
  Purchase #4 $62.45   6.331%   $66.4037   $66.40   $66.40   $66.40  
  Purchase #5 $62.36   6.695%   $66.535   $66.54   $66.55   $66.50  
  Purchase #6 $216.67   9.250%   $236.712   $236.71   $236.70   $236.70  
  Purchase #7 $12.55   3.825%   $13.03   $13.03   $13.05   $13.00  
  7 purchase totals = $710.13       $771.0398   $771.03   $771.05   $771.00