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 $84.57   13.437%   $95.9337   $95.93   $95.95   $95.90  
  Purchase #2 $181.88   11.664%   $203.0945   $203.09   $203.10   $203.10  
  Purchase #3 $172.72   9.226%   $188.6551   $188.66   $188.65   $188.70  
  Purchase #4 $61.29   12.513%   $68.9592   $68.96   $68.95   $69.00  
  Purchase #5 $207.94   10.365%   $229.493   $229.49   $229.50   $229.50  
  Purchase #6 $217.46   5.800%   $230.0727   $230.07   $230.05   $230.10  
  Purchase #7 $249.70   8.293%   $270.4076   $270.41   $270.40   $270.40  
  7 purchase totals = $1,175.56       $1,286.6158   $1,286.61   $1,286.60   $1,286.70