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 $161.70   9.530%   $177.11   $177.11   $177.10   $177.10  
  Purchase #2 $236.53   8.873%   $257.5173   $257.52   $257.50   $257.50  
  Purchase #3 $94.41   11.811%   $105.5608   $105.56   $105.55   $105.60  
  Purchase #4 $136.68   11.539%   $152.4515   $152.45   $152.45   $152.50  
  Purchase #5 $212.74   11.369%   $236.9264   $236.93   $236.95   $236.90  
  Purchase #6 $188.88   9.715%   $207.2297   $207.23   $207.25   $207.20  
  Purchase #7 $183.58   3.595%   $190.1797   $190.18   $190.20   $190.20  
  7 purchase totals = $1,214.52       $1,326.9754   $1,326.98   $1,327.00   $1,327.00