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 $181.93   8.794%   $197.9289   $197.93   $197.95   $197.90  
  Purchase #2 $45.96   7.231%   $49.2834   $49.28   $49.30   $49.30  
  Purchase #3 $16.33   6.823%   $17.4442   $17.44   $17.45   $17.40  
  Purchase #4 $55.41   13.633%   $62.964   $62.96   $62.95   $63.00  
  Purchase #5 $196.52   6.160%   $208.6256   $208.63   $208.65   $208.60  
  Purchase #6 $188.45   9.836%   $206.9859   $206.99   $207.00   $207.00  
  Purchase #7 $113.76   7.571%   $122.3728   $122.37   $122.35   $122.40  
  7 purchase totals = $798.36       $865.6048   $865.60   $865.65   $865.60