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 $227.35   9.186%   $248.2344   $248.23   $248.25   $248.20  
  Purchase #2 $218.67   6.567%   $233.0301   $233.03   $233.05   $233.00  
  Purchase #3 $201.83   6.458%   $214.8642   $214.86   $214.85   $214.90  
  Purchase #4 $191.85   3.718%   $198.983   $198.98   $199.00   $199.00  
  Purchase #5 $59.64   5.719%   $63.0508   $63.05   $63.05   $63.10  
  Purchase #6 $60.26   13.705%   $68.5186   $68.52   $68.50   $68.50  
  Purchase #7 $177.71   3.178%   $183.3576   $183.36   $183.35   $183.40  
  7 purchase totals = $1,137.31       $1,210.0387   $1,210.03   $1,210.05   $1,210.10