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 $176.65   10.670%   $195.4986   $195.50   $195.50   $195.50  
  Purchase #2 $180.95   3.724%   $187.6886   $187.69   $187.70   $187.70  
  Purchase #3 $17.52   8.379%   $18.988   $18.99   $19.00   $19.00  
  Purchase #4 $56.31   5.852%   $59.6053   $59.61   $59.60   $59.60  
  Purchase #5 $54.75   3.451%   $56.6394   $56.64   $56.65   $56.60  
  Purchase #6 $14.43   12.823%   $16.2804   $16.28   $16.30   $16.30  
  Purchase #7 $235.50   7.746%   $253.7418   $253.74   $253.75   $253.70  
  7 purchase totals = $736.11       $788.4421   $788.45   $788.50   $788.40