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 $237.85   10.410%   $262.6102   $262.61   $262.60   $262.60  
  Purchase #2 $205.77   12.688%   $231.8781   $231.88   $231.90   $231.90  
  Purchase #3 $193.65   4.552%   $202.4649   $202.46   $202.45   $202.50  
  Purchase #4 $7.58   8.630%   $8.2342   $8.23   $8.25   $8.20  
  Purchase #5 $197.50   4.720%   $206.822   $206.82   $206.80   $206.80  
  Purchase #6 $13.52   3.572%   $14.0029   $14.00   $14.00   $14.00  
  Purchase #7 $107.31   13.685%   $121.9954   $122.00   $122.00   $122.00  
  7 purchase totals = $963.18       $1,048.0077   $1,048.00   $1,048.00   $1,048.00