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 $116.26   5.459%   $122.6066   $122.61   $122.60   $122.60  
  Purchase #2 $191.80   13.848%   $218.3605   $218.36   $218.35   $218.40  
  Purchase #3 $158.51   13.432%   $179.8011   $179.80   $179.80   $179.80  
  Purchase #4 $236.58   6.741%   $252.5279   $252.53   $252.55   $252.50  
  Purchase #5 $38.39   7.271%   $41.1813   $41.18   $41.20   $41.20  
  Purchase #6 $171.51   10.796%   $190.0262   $190.03   $190.05   $190.00  
  Purchase #7 $25.77   10.873%   $28.572   $28.57   $28.55   $28.60  
  7 purchase totals = $938.82       $1,033.0756   $1,033.08   $1,033.10   $1,033.10