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 $57.90   7.627%   $62.316   $62.32   $62.30   $62.30  
  Purchase #2 $119.99   11.256%   $133.4961   $133.50   $133.50   $133.50  
  Purchase #3 $198.42   5.733%   $209.7954   $209.80   $209.80   $209.80  
  Purchase #4 $31.81   12.855%   $35.8992   $35.90   $35.90   $35.90  
  Purchase #5 $186.76   7.583%   $200.922   $200.92   $200.90   $200.90  
  Purchase #6 $223.34   4.668%   $233.7655   $233.77   $233.75   $233.80  
  Purchase #7 $227.68   10.627%   $251.8756   $251.88   $251.90   $251.90  
  7 purchase totals = $1,045.90       $1,128.0698   $1,128.09   $1,128.05   $1,128.10