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 $156.43   11.622%   $174.6103   $174.61   $174.60   $174.60  
  Purchase #2 $147.88   10.602%   $163.5582   $163.56   $163.55   $163.60  
  Purchase #3 $23.95   11.596%   $26.7272   $26.73   $26.75   $26.70  
  Purchase #4 $94.51   7.668%   $101.757   $101.76   $101.75   $101.80  
  Purchase #5 $228.92   3.317%   $236.5133   $236.51   $236.50   $236.50  
  Purchase #6 $216.40   12.178%   $242.7532   $242.75   $242.75   $242.80  
  Purchase #7 $190.25   8.113%   $205.685   $205.69   $205.70   $205.70  
  7 purchase totals = $1,058.34       $1,151.6042   $1,151.61   $1,151.60   $1,151.70