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 $212.63   6.650%   $226.7699   $226.77   $226.75   $226.80  
  Purchase #2 $143.65   10.845%   $159.2288   $159.23   $159.25   $159.20  
  Purchase #3 $54.88   12.124%   $61.5337   $61.53   $61.55   $61.50  
  Purchase #4 $98.54   4.233%   $102.7112   $102.71   $102.70   $102.70  
  Purchase #5 $250.85   4.450%   $262.0128   $262.01   $262.00   $262.00  
  Purchase #6 $187.47   11.263%   $208.5847   $208.58   $208.60   $208.60  
  Purchase #7 $119.95   10.357%   $132.3732   $132.37   $132.35   $132.40  
  7 purchase totals = $1,067.97       $1,153.2143   $1,153.20   $1,153.20   $1,153.20