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 $57.96   7.643%   $62.3899   $62.39   $62.40   $62.40  
  Purchase #2 $208.66   8.799%   $227.02   $227.02   $227.00   $227.00  
  Purchase #3 $237.82   5.654%   $251.2663   $251.27   $251.25   $251.30  
  Purchase #4 $76.61   4.300%   $79.9042   $79.90   $79.90   $79.90  
  Purchase #5 $193.68   12.196%   $217.3012   $217.30   $217.30   $217.30  
  Purchase #6 $185.62   3.327%   $191.7956   $191.80   $191.80   $191.80  
  Purchase #7 $233.58   13.718%   $265.6225   $265.62   $265.60   $265.60  
  7 purchase totals = $1,193.93       $1,295.2997   $1,295.30   $1,295.25   $1,295.30