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 $108.74   5.710%   $114.9491   $114.95   $114.95   $114.90  
  Purchase #2 $52.93   11.827%   $59.19   $59.19   $59.20   $59.20  
  Purchase #3 $199.90   10.421%   $220.7316   $220.73   $220.75   $220.70  
  Purchase #4 $182.72   11.376%   $203.5062   $203.51   $203.50   $203.50  
  Purchase #5 $107.86   8.745%   $117.2924   $117.29   $117.30   $117.30  
  Purchase #6 $207.62   13.809%   $236.2902   $236.29   $236.30   $236.30  
  Purchase #7 $64.60   8.823%   $70.2997   $70.30   $70.30   $70.30  
  7 purchase totals = $924.37       $1,022.2592   $1,022.26   $1,022.30   $1,022.20