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 $224.66   5.587%   $237.2118   $237.21   $237.20   $237.20  
  Purchase #2 $236.48   3.758%   $245.3669   $245.37   $245.35   $245.40  
  Purchase #3 $190.76   11.584%   $212.8576   $212.86   $212.85   $212.90  
  Purchase #4 $109.88   13.385%   $124.5874   $124.59   $124.60   $124.60  
  Purchase #5 $206.90   13.253%   $234.3205   $234.32   $234.30   $234.30  
  Purchase #6 $141.65   8.717%   $153.9976   $154.00   $154.00   $154.00  
  Purchase #7 $216.35   5.380%   $227.9896   $227.99   $228.00   $228.00  
  7 purchase totals = $1,326.68       $1,436.3314   $1,436.34   $1,436.30   $1,436.40