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 $221.45   10.550%   $244.813   $244.81   $244.80   $244.80  
  Purchase #2 $235.48   10.653%   $260.5657   $260.57   $260.55   $260.60  
  Purchase #3 $23.99   12.703%   $27.0374   $27.04   $27.05   $27.00  
  Purchase #4 $75.40   8.822%   $82.0518   $82.05   $82.05   $82.10  
  Purchase #5 $66.41   8.321%   $71.936   $71.94   $71.95   $71.90  
  Purchase #6 $219.89   7.778%   $236.993   $236.99   $237.00   $237.00  
  Purchase #7 $195.25   11.387%   $217.4831   $217.48   $217.50   $217.50  
  7 purchase totals = $1,037.87       $1,140.8800   $1,140.88   $1,140.90   $1,140.90