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 $164.36   11.273%   $182.8883   $182.89   $182.90   $182.90  
  Purchase #2 $217.38   11.568%   $242.5265   $242.53   $242.55   $242.50  
  Purchase #3 $13.52   9.259%   $14.7718   $14.77   $14.75   $14.80  
  Purchase #4 $86.57   10.526%   $95.6824   $95.68   $95.70   $95.70  
  Purchase #5 $236.43   13.325%   $267.9343   $267.93   $267.95   $267.90  
  Purchase #6 $207.91   13.301%   $235.5641   $235.56   $235.55   $235.60  
  Purchase #7 $26.65   7.167%   $28.56   $28.56   $28.55   $28.60  
  7 purchase totals = $952.82       $1,067.9274   $1,067.92   $1,067.95   $1,068.00