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 $55.26   12.287%   $62.0498   $62.05   $62.05   $62.00  
  Purchase #2 $239.99   4.244%   $250.1752   $250.18   $250.20   $250.20  
  Purchase #3 $237.59   7.494%   $255.395   $255.40   $255.40   $255.40  
  Purchase #4 $240.47   4.271%   $250.7405   $250.74   $250.75   $250.70  
  Purchase #5 $127.57   10.412%   $140.8526   $140.85   $140.85   $140.90  
  Purchase #6 $167.28   6.311%   $177.837   $177.84   $177.85   $177.80  
  Purchase #7 $141.91   11.208%   $157.8153   $157.82   $157.80   $157.80  
  7 purchase totals = $1,210.07       $1,294.8654   $1,294.88   $1,294.90   $1,294.80