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 $222.49   3.488%   $230.2505   $230.25   $230.25   $230.30  
  Purchase #2 $216.58   13.167%   $245.0971   $245.10   $245.10   $245.10  
  Purchase #3 $54.63   9.557%   $59.851   $59.85   $59.85   $59.90  
  Purchase #4 $234.58   8.523%   $254.5733   $254.57   $254.55   $254.60  
  Purchase #5 $51.56   12.555%   $58.0334   $58.03   $58.05   $58.00  
  Purchase #6 $57.82   7.382%   $62.0883   $62.09   $62.10   $62.10  
  Purchase #7 $195.73   10.352%   $215.992   $215.99   $216.00   $216.00  
  7 purchase totals = $1,033.39       $1,125.8856   $1,125.88   $1,125.90   $1,126.00