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 $211.76   5.299%   $222.9812   $222.98   $223.00   $223.00  
  Purchase #2 $126.55   9.247%   $138.2521   $138.25   $138.25   $138.30  
  Purchase #3 $7.59   4.281%   $7.9149   $7.91   $7.90   $7.90  
  Purchase #4 $191.72   11.398%   $213.5722   $213.57   $213.55   $213.60  
  Purchase #5 $35.62   8.759%   $38.74   $38.74   $38.75   $38.70  
  Purchase #6 $136.84   5.517%   $144.3895   $144.39   $144.40   $144.40  
  Purchase #7 $240.61   3.247%   $248.4226   $248.42   $248.40   $248.40  
  7 purchase totals = $950.69       $1,014.2725   $1,014.26   $1,014.25   $1,014.30