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 $212.98   9.513%   $233.2408   $233.24   $233.25   $233.20  
  Purchase #2 $14.75   12.768%   $16.6333   $16.63   $16.65   $16.60  
  Purchase #3 $215.66   10.686%   $238.7054   $238.71   $238.70   $238.70  
  Purchase #4 $90.88   11.376%   $101.2185   $101.22   $101.20   $101.20  
  Purchase #5 $163.65   6.484%   $174.2611   $174.26   $174.25   $174.30  
  Purchase #6 $68.78   6.790%   $73.4502   $73.45   $73.45   $73.50  
  Purchase #7 $188.48   10.738%   $208.719   $208.72   $208.70   $208.70  
  7 purchase totals = $955.18       $1,046.2283   $1,046.23   $1,046.20   $1,046.20