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 $147.83   3.366%   $152.806   $152.81   $152.80   $152.80  
  Purchase #2 $134.95   10.392%   $148.974   $148.97   $148.95   $149.00  
  Purchase #3 $75.88   3.720%   $78.7027   $78.70   $78.70   $78.70  
  Purchase #4 $179.58   7.433%   $192.9282   $192.93   $192.95   $192.90  
  Purchase #5 $43.52   11.481%   $48.5165   $48.52   $48.50   $48.50  
  Purchase #6 $237.70   6.563%   $253.3003   $253.30   $253.30   $253.30  
  Purchase #7 $191.58   4.743%   $200.6666   $200.67   $200.65   $200.70  
  7 purchase totals = $1,011.04       $1,075.8943   $1,075.90   $1,075.85   $1,075.90