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 $87.53   5.448%   $92.2986   $92.30   $92.30   $92.30  
  Purchase #2 $89.47   4.292%   $93.3101   $93.31   $93.30   $93.30  
  Purchase #3 $52.37   8.732%   $56.9429   $56.94   $56.95   $56.90  
  Purchase #4 $164.71   8.585%   $178.8504   $178.85   $178.85   $178.90  
  Purchase #5 $231.91   7.276%   $248.7838   $248.78   $248.80   $248.80  
  Purchase #6 $177.51   12.248%   $199.2514   $199.25   $199.25   $199.30  
  Purchase #7 $239.28   9.556%   $262.1456   $262.15   $262.15   $262.10  
  7 purchase totals = $1,042.78       $1,131.5828   $1,131.58   $1,131.60   $1,131.60