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 $34.89   10.243%   $38.4638   $38.46   $38.45   $38.50  
  Purchase #2 $220.48   6.864%   $235.6137   $235.61   $235.60   $235.60  
  Purchase #3 $59.77   4.114%   $62.2289   $62.23   $62.25   $62.20  
  Purchase #4 $241.78   4.514%   $252.6939   $252.69   $252.70   $252.70  
  Purchase #5 $207.34   9.291%   $226.604   $226.60   $226.60   $226.60  
  Purchase #6 $101.85   5.701%   $107.6565   $107.66   $107.65   $107.70  
  Purchase #7 $189.62   3.720%   $196.6739   $196.67   $196.65   $196.70  
  7 purchase totals = $1,055.73       $1,119.9347   $1,119.92   $1,119.90   $1,120.00