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 $92.75   3.418%   $95.9202   $95.92   $95.90   $95.90  
  Purchase #2 $220.29   7.427%   $236.6509   $236.65   $236.65   $236.70  
  Purchase #3 $61.25   4.537%   $64.0289   $64.03   $64.05   $64.00  
  Purchase #4 $38.78   12.570%   $43.6546   $43.65   $43.65   $43.70  
  Purchase #5 $141.29   4.396%   $147.5011   $147.50   $147.50   $147.50  
  Purchase #6 $159.64   8.169%   $172.681   $172.68   $172.70   $172.70  
  Purchase #7 $38.81   10.848%   $43.0201   $43.02   $43.00   $43.00  
  7 purchase totals = $752.81       $803.4568   $803.45   $803.45   $803.50