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 $82.71   4.567%   $86.4874   $86.49   $86.50   $86.50  
  Purchase #2 $160.71   8.585%   $174.507   $174.51   $174.50   $174.50  
  Purchase #3 $208.65   12.854%   $235.4699   $235.47   $235.45   $235.50  
  Purchase #4 $167.69   12.569%   $188.767   $188.77   $188.75   $188.80  
  Purchase #5 $67.48   8.501%   $73.2165   $73.22   $73.20   $73.20  
  Purchase #6 $179.37   12.380%   $201.576   $201.58   $201.60   $201.60  
  Purchase #7 $195.91   5.660%   $206.9985   $207.00   $207.00   $207.00  
  7 purchase totals = $1,062.52       $1,167.0223   $1,167.04   $1,167.00   $1,167.10