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 $41.35   5.627%   $43.6768   $43.68   $43.70   $43.70  
  Purchase #2 $143.95   9.692%   $157.9016   $157.90   $157.90   $157.90  
  Purchase #3 $189.30   8.808%   $205.9735   $205.97   $205.95   $206.00  
  Purchase #4 $208.84   11.293%   $232.4243   $232.42   $232.40   $232.40  
  Purchase #5 $27.25   10.850%   $30.2066   $30.21   $30.20   $30.20  
  Purchase #6 $146.82   3.150%   $151.4448   $151.44   $151.45   $151.40  
  Purchase #7 $69.83   4.235%   $72.7873   $72.79   $72.80   $72.80  
  7 purchase totals = $827.34       $894.4149   $894.41   $894.40   $894.40