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 $186.83   8.310%   $202.3556   $202.36   $202.35   $202.40  
  Purchase #2 $112.93   9.469%   $123.6233   $123.62   $123.60   $123.60  
  Purchase #3 $46.43   11.364%   $51.7063   $51.71   $51.70   $51.70  
  Purchase #4 $111.83   10.617%   $123.703   $123.70   $123.70   $123.70  
  Purchase #5 $244.31   9.838%   $268.3452   $268.35   $268.35   $268.30  
  Purchase #6 $212.25   4.486%   $221.7715   $221.77   $221.75   $221.80  
  Purchase #7 $17.49   11.401%   $19.484   $19.48   $19.50   $19.50  
  7 purchase totals = $932.07       $1,010.9889   $1,010.99   $1,010.95   $1,011.00