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 $208.42   8.448%   $226.0273   $226.03   $226.05   $226.00  
  Purchase #2 $237.85   11.493%   $265.1861   $265.19   $265.20   $265.20  
  Purchase #3 $160.74   4.533%   $168.0263   $168.03   $168.05   $168.00  
  Purchase #4 $39.64   11.477%   $44.1895   $44.19   $44.20   $44.20  
  Purchase #5 $130.75   12.142%   $146.6257   $146.63   $146.65   $146.60  
  Purchase #6 $64.29   11.102%   $71.4275   $71.43   $71.45   $71.40  
  Purchase #7 $198.27   6.550%   $211.2567   $211.26   $211.25   $211.30  
  7 purchase totals = $1,039.96       $1,132.7391   $1,132.76   $1,132.85   $1,132.70