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 $59.80   13.274%   $67.7379   $67.74   $67.75   $67.70  
  Purchase #2 $163.29   7.148%   $174.962   $174.96   $174.95   $175.00  
  Purchase #3 $245.76   8.408%   $266.4235   $266.42   $266.40   $266.40  
  Purchase #4 $186.92   11.669%   $208.7317   $208.73   $208.75   $208.70  
  Purchase #5 $185.60   4.159%   $193.3191   $193.32   $193.30   $193.30  
  Purchase #6 $8.68   11.682%   $9.694   $9.69   $9.70   $9.70  
  Purchase #7 $112.99   11.723%   $126.2358   $126.24   $126.25   $126.20  
  7 purchase totals = $963.04       $1,047.1040   $1,047.10   $1,047.10   $1,047.00