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 $54.25   10.495%   $59.9435   $59.94   $59.95   $59.90  
  Purchase #2 $169.71   13.519%   $192.6531   $192.65   $192.65   $192.70  
  Purchase #3 $76.46   12.873%   $86.3027   $86.30   $86.30   $86.30  
  Purchase #4 $189.28   4.828%   $198.4184   $198.42   $198.40   $198.40  
  Purchase #5 $194.88   12.762%   $219.7506   $219.75   $219.75   $219.80  
  Purchase #6 $53.67   4.252%   $55.952   $55.95   $55.95   $56.00  
  Purchase #7 $45.25   5.427%   $47.7057   $47.71   $47.70   $47.70  
  7 purchase totals = $783.50       $860.7260   $860.72   $860.70   $860.80