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 $248.45   7.158%   $266.2341   $266.23   $266.25   $266.20  
  Purchase #2 $80.92   7.513%   $86.9995   $87.00   $87.00   $87.00  
  Purchase #3 $33.33   5.492%   $35.1605   $35.16   $35.15   $35.20  
  Purchase #4 $75.69   10.189%   $83.4021   $83.40   $83.40   $83.40  
  Purchase #5 $208.65   12.484%   $234.6979   $234.70   $234.70   $234.70  
  Purchase #6 $191.86   9.552%   $210.1865   $210.19   $210.20   $210.20  
  Purchase #7 $185.69   6.405%   $197.5834   $197.58   $197.60   $197.60  
  7 purchase totals = $1,024.59       $1,114.2640   $1,114.26   $1,114.30   $1,114.30