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 $57.95   5.704%   $61.2555   $61.26   $61.25   $61.30  
  Purchase #2 $168.94   7.730%   $181.9991   $182.00   $182.00   $182.00  
  Purchase #3 $120.53   12.375%   $135.4456   $135.45   $135.45   $135.40  
  Purchase #4 $235.73   10.255%   $259.9041   $259.90   $259.90   $259.90  
  Purchase #5 $209.85   3.517%   $217.2304   $217.23   $217.25   $217.20  
  Purchase #6 $43.67   5.855%   $46.2269   $46.23   $46.25   $46.20  
  Purchase #7 $175.62   10.724%   $194.4535   $194.45   $194.45   $194.50  
  7 purchase totals = $1,012.29       $1,096.5151   $1,096.52   $1,096.55   $1,096.50