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 $87.73   8.302%   $95.0133   $95.01   $95.00   $95.00  
  Purchase #2 $191.94   12.380%   $215.7022   $215.70   $215.70   $215.70  
  Purchase #3 $218.81   8.291%   $236.9515   $236.95   $236.95   $237.00  
  Purchase #4 $249.30   13.477%   $282.8982   $282.90   $282.90   $282.90  
  Purchase #5 $57.79   11.615%   $64.5023   $64.50   $64.50   $64.50  
  Purchase #6 $163.81   9.424%   $179.2475   $179.25   $179.25   $179.20  
  Purchase #7 $93.36   4.563%   $97.62   $97.62   $97.60   $97.60  
  7 purchase totals = $1,062.74       $1,171.9350   $1,171.93   $1,171.90   $1,171.90