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 $93.86   9.325%   $102.6124   $102.61   $102.60   $102.60  
  Purchase #2 $106.78   8.626%   $115.9908   $115.99   $116.00   $116.00  
  Purchase #3 $147.47   9.625%   $161.664   $161.66   $161.65   $161.70  
  Purchase #4 $107.83   13.194%   $122.0571   $122.06   $122.05   $122.10  
  Purchase #5 $141.35   13.861%   $160.9425   $160.94   $160.95   $160.90  
  Purchase #6 $45.55   6.486%   $48.5044   $48.50   $48.50   $48.50  
  Purchase #7 $141.61   6.823%   $151.2721   $151.27   $151.25   $151.30  
  7 purchase totals = $784.45       $863.0433   $863.03   $863.00   $863.10