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 $176.53   11.327%   $196.5256   $196.53   $196.55   $196.50  
  Purchase #2 $167.96   5.551%   $177.2835   $177.28   $177.30   $177.30  
  Purchase #3 $130.32   5.833%   $137.9216   $137.92   $137.90   $137.90  
  Purchase #4 $239.91   4.439%   $250.5596   $250.56   $250.55   $250.60  
  Purchase #5 $142.31   4.223%   $148.3198   $148.32   $148.30   $148.30  
  Purchase #6 $174.99   10.716%   $193.7419   $193.74   $193.75   $193.70  
  Purchase #7 $232.87   8.386%   $252.3985   $252.40   $252.40   $252.40  
  7 purchase totals = $1,264.89       $1,356.7505   $1,356.75   $1,356.75   $1,356.70