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 $41.28   5.579%   $43.583   $43.58   $43.60   $43.60  
  Purchase #2 $194.56   10.811%   $215.5939   $215.59   $215.60   $215.60  
  Purchase #3 $70.56   8.442%   $76.5167   $76.52   $76.50   $76.50  
  Purchase #4 $64.30   3.447%   $66.5164   $66.52   $66.50   $66.50  
  Purchase #5 $236.38   13.387%   $268.0242   $268.02   $268.00   $268.00  
  Purchase #6 $133.37   5.168%   $140.2626   $140.26   $140.25   $140.30  
  Purchase #7 $213.30   11.139%   $237.0595   $237.06   $237.05   $237.10  
  7 purchase totals = $953.75       $1,047.5563   $1,047.55   $1,047.50   $1,047.60