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 $193.97   6.565%   $206.7041   $206.70   $206.70   $206.70  
  Purchase #2 $70.62   3.400%   $73.0211   $73.02   $73.00   $73.00  
  Purchase #3 $84.41   4.481%   $88.1924   $88.19   $88.20   $88.20  
  Purchase #4 $158.54   6.526%   $168.8863   $168.89   $168.90   $168.90  
  Purchase #5 $213.55   12.872%   $241.0382   $241.04   $241.05   $241.00  
  Purchase #6 $236.30   9.709%   $259.2424   $259.24   $259.25   $259.20  
  Purchase #7 $211.49   3.173%   $218.2006   $218.20   $218.20   $218.20  
  7 purchase totals = $1,168.88       $1,255.2851   $1,255.28   $1,255.30   $1,255.20