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 $43.58   9.309%   $47.6369   $47.64   $47.65   $47.60  
  Purchase #2 $182.81   9.737%   $200.6102   $200.61   $200.60   $200.60  
  Purchase #3 $36.36   11.183%   $40.4261   $40.43   $40.45   $40.40  
  Purchase #4 $172.62   3.755%   $179.1019   $179.10   $179.10   $179.10  
  Purchase #5 $93.57   11.292%   $104.1359   $104.14   $104.15   $104.10  
  Purchase #6 $164.71   11.346%   $183.398   $183.40   $183.40   $183.40  
  Purchase #7 $244.30   10.162%   $269.1258   $269.13   $269.15   $269.10  
  7 purchase totals = $937.95       $1,024.4348   $1,024.45   $1,024.50   $1,024.30