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 $215.95   9.206%   $235.8304   $235.83   $235.85   $235.80  
  Purchase #2 $166.86   6.195%   $177.197   $177.20   $177.20   $177.20  
  Purchase #3 $6.71   7.640%   $7.2226   $7.22   $7.20   $7.20  
  Purchase #4 $182.29   10.108%   $200.7159   $200.72   $200.70   $200.70  
  Purchase #5 $178.58   5.661%   $188.6894   $188.69   $188.70   $188.70  
  Purchase #6 $217.59   3.845%   $225.9563   $225.96   $225.95   $226.00  
  Purchase #7 $58.83   3.734%   $61.0267   $61.03   $61.05   $61.00  
  7 purchase totals = $1,026.81       $1,096.6383   $1,096.65   $1,096.65   $1,096.60