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 $126.98   11.706%   $141.8443   $141.84   $141.85   $141.80  
  Purchase #2 $236.28   9.198%   $258.013   $258.01   $258.00   $258.00  
  Purchase #3 $226.77   9.418%   $248.1272   $248.13   $248.15   $248.10  
  Purchase #4 $163.92   7.734%   $176.5976   $176.60   $176.60   $176.60  
  Purchase #5 $125.30   4.806%   $131.3219   $131.32   $131.30   $131.30  
  Purchase #6 $69.55   9.629%   $76.247   $76.25   $76.25   $76.20  
  Purchase #7 $184.57   9.704%   $202.4807   $202.48   $202.50   $202.50  
  7 purchase totals = $1,133.37       $1,234.6317   $1,234.63   $1,234.65   $1,234.50