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 $230.62   13.710%   $262.238   $262.24   $262.25   $262.20  
  Purchase #2 $82.82   3.278%   $85.5348   $85.53   $85.55   $85.50  
  Purchase #3 $74.59   9.688%   $81.8163   $81.82   $81.80   $81.80  
  Purchase #4 $108.83   3.388%   $112.5172   $112.52   $112.50   $112.50  
  Purchase #5 $138.69   7.221%   $148.7048   $148.70   $148.70   $148.70  
  Purchase #6 $248.60   4.445%   $259.6503   $259.65   $259.65   $259.70  
  Purchase #7 $122.93   7.164%   $131.7367   $131.74   $131.75   $131.70  
  7 purchase totals = $1,007.08       $1,082.1981   $1,082.20   $1,082.20   $1,082.10