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 $212.74   6.719%   $227.034   $227.03   $227.05   $227.00  
  Purchase #2 $88.46   11.476%   $98.6117   $98.61   $98.60   $98.60  
  Purchase #3 $232.88   7.448%   $250.2249   $250.22   $250.20   $250.20  
  Purchase #4 $169.94   6.151%   $180.393   $180.39   $180.40   $180.40  
  Purchase #5 $164.29   5.178%   $172.7969   $172.80   $172.80   $172.80  
  Purchase #6 $65.79   5.838%   $69.6308   $69.63   $69.65   $69.60  
  Purchase #7 $237.41   12.692%   $267.5421   $267.54   $267.55   $267.50  
  7 purchase totals = $1,171.51       $1,266.2334   $1,266.22   $1,266.25   $1,266.10