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 $86.41   6.529%   $92.0517   $92.05   $92.05   $92.10  
  Purchase #2 $73.36   4.575%   $76.7162   $76.72   $76.70   $76.70  
  Purchase #3 $248.87   7.866%   $268.4461   $268.45   $268.45   $268.40  
  Purchase #4 $109.65   9.239%   $119.7806   $119.78   $119.80   $119.80  
  Purchase #5 $196.82   5.467%   $207.5801   $207.58   $207.60   $207.60  
  Purchase #6 $180.79   11.855%   $202.2227   $202.22   $202.20   $202.20  
  Purchase #7 $89.91   8.517%   $97.5676   $97.57   $97.55   $97.60  
  7 purchase totals = $985.81       $1,064.3650   $1,064.37   $1,064.35   $1,064.40