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 $33.62   6.871%   $35.93   $35.93   $35.95   $35.90  
  Purchase #2 $200.99   6.489%   $214.0322   $214.03   $214.05   $214.00  
  Purchase #3 $14.56   7.211%   $15.6099   $15.61   $15.60   $15.60  
  Purchase #4 $199.29   7.671%   $214.5775   $214.58   $214.60   $214.60  
  Purchase #5 $51.83   13.803%   $58.9841   $58.98   $59.00   $59.00  
  Purchase #6 $242.54   8.226%   $262.4913   $262.49   $262.50   $262.50  
  Purchase #7 $92.91   11.717%   $103.7963   $103.80   $103.80   $103.80  
  7 purchase totals = $835.74       $905.4213   $905.42   $905.50   $905.40