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 $190.46   11.662%   $212.6714   $212.67   $212.65   $212.70  
  Purchase #2 $116.25   8.827%   $126.5114   $126.51   $126.50   $126.50  
  Purchase #3 $69.89   9.199%   $76.3192   $76.32   $76.30   $76.30  
  Purchase #4 $210.86   13.488%   $239.3008   $239.30   $239.30   $239.30  
  Purchase #5 $124.25   6.444%   $132.2567   $132.26   $132.25   $132.30  
  Purchase #6 $22.49   4.305%   $23.4582   $23.46   $23.45   $23.50  
  Purchase #7 $176.69   13.836%   $201.1368   $201.14   $201.15   $201.10  
  7 purchase totals = $910.89       $1,011.6545   $1,011.66   $1,011.60   $1,011.70