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 $114.41   10.691%   $126.6416   $126.64   $126.65   $126.60  
  Purchase #2 $235.66   8.749%   $256.2779   $256.28   $256.30   $256.30  
  Purchase #3 $60.35   8.862%   $65.6982   $65.70   $65.70   $65.70  
  Purchase #4 $226.56   5.786%   $239.6688   $239.67   $239.65   $239.70  
  Purchase #5 $158.69   5.354%   $167.1863   $167.19   $167.20   $167.20  
  Purchase #6 $127.42   5.248%   $134.107   $134.11   $134.10   $134.10  
  Purchase #7 $97.35   11.567%   $108.6105   $108.61   $108.60   $108.60  
  7 purchase totals = $1,020.44       $1,098.1903   $1,098.20   $1,098.20   $1,098.20