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 $208.52   7.742%   $224.6636   $224.66   $224.65   $224.70  
  Purchase #2 $248.67   11.541%   $277.369   $277.37   $277.35   $277.40  
  Purchase #3 $22.86   9.379%   $25.004   $25.00   $25.00   $25.00  
  Purchase #4 $141.80   7.757%   $152.7994   $152.80   $152.80   $152.80  
  Purchase #5 $13.46   9.280%   $14.7091   $14.71   $14.70   $14.70  
  Purchase #6 $158.63   9.680%   $173.9854   $173.99   $174.00   $174.00  
  Purchase #7 $185.83   5.869%   $196.7364   $196.74   $196.75   $196.70  
  7 purchase totals = $979.77       $1,065.2669   $1,065.27   $1,065.25   $1,065.30