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 $208.50   3.285%   $215.3492   $215.35   $215.35   $215.30  
  Purchase #2 $225.62   11.243%   $250.9865   $250.99   $251.00   $251.00  
  Purchase #3 $202.56   5.258%   $213.2106   $213.21   $213.20   $213.20  
  Purchase #4 $59.37   3.659%   $61.5423   $61.54   $61.55   $61.50  
  Purchase #5 $238.30   11.488%   $265.6759   $265.68   $265.70   $265.70  
  Purchase #6 $210.88   9.293%   $230.4771   $230.48   $230.50   $230.50  
  Purchase #7 $248.79   3.638%   $257.841   $257.84   $257.85   $257.80  
  7 purchase totals = $1,394.02       $1,495.0826   $1,495.09   $1,495.15   $1,495.00