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 $187.94   7.160%   $201.3965   $201.40   $201.40   $201.40  
  Purchase #2 $181.71   13.196%   $205.6885   $205.69   $205.70   $205.70  
  Purchase #3 $24.81   7.265%   $26.6124   $26.61   $26.60   $26.60  
  Purchase #4 $248.32   5.644%   $262.3352   $262.34   $262.35   $262.30  
  Purchase #5 $166.63   6.621%   $177.6626   $177.66   $177.65   $177.70  
  Purchase #6 $87.35   12.359%   $98.1456   $98.15   $98.15   $98.10  
  Purchase #7 $65.71   7.195%   $70.4378   $70.44   $70.45   $70.40  
  7 purchase totals = $962.47       $1,042.2786   $1,042.29   $1,042.30   $1,042.20