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 $206.55   9.542%   $226.259   $226.26   $226.25   $226.30  
  Purchase #2 $173.90   12.358%   $195.3906   $195.39   $195.40   $195.40  
  Purchase #3 $165.81   4.378%   $173.0692   $173.07   $173.05   $173.10  
  Purchase #4 $183.73   9.788%   $201.7135   $201.71   $201.70   $201.70  
  Purchase #5 $105.99   3.133%   $109.3107   $109.31   $109.30   $109.30  
  Purchase #6 $32.34   4.434%   $33.774   $33.77   $33.75   $33.80  
  Purchase #7 $190.72   5.405%   $201.0284   $201.03   $201.05   $201.00  
  7 purchase totals = $1,059.04       $1,140.5454   $1,140.54   $1,140.50   $1,140.60