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 $55.49   11.839%   $62.0595   $62.06   $62.05   $62.10  
  Purchase #2 $201.43   12.209%   $226.0226   $226.02   $226.00   $226.00  
  Purchase #3 $180.83   4.646%   $189.2314   $189.23   $189.25   $189.20  
  Purchase #4 $194.47   10.753%   $215.3814   $215.38   $215.40   $215.40  
  Purchase #5 $15.65   5.621%   $16.5297   $16.53   $16.55   $16.50  
  Purchase #6 $189.46   8.335%   $205.2515   $205.25   $205.25   $205.30  
  Purchase #7 $43.42   4.849%   $45.5254   $45.53   $45.55   $45.50  
  7 purchase totals = $880.75       $960.0015   $960.00   $960.05   $960.00