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 $201.26   6.792%   $214.9296   $214.93   $214.95   $214.90  
  Purchase #2 $49.58   13.344%   $56.196   $56.20   $56.20   $56.20  
  Purchase #3 $172.46   11.705%   $192.6464   $192.65   $192.65   $192.60  
  Purchase #4 $141.31   12.682%   $159.2309   $159.23   $159.25   $159.20  
  Purchase #5 $208.95   5.814%   $221.0984   $221.10   $221.10   $221.10  
  Purchase #6 $117.55   10.260%   $129.6106   $129.61   $129.60   $129.60  
  Purchase #7 $35.31   8.102%   $38.1708   $38.17   $38.15   $38.20  
  7 purchase totals = $926.42       $1,011.8827   $1,011.89   $1,011.90   $1,011.80