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 $195.65   5.109%   $205.6458   $205.65   $205.65   $205.60  
  Purchase #2 $41.96   4.855%   $43.9972   $44.00   $44.00   $44.00  
  Purchase #3 $187.25   7.685%   $201.6402   $201.64   $201.65   $201.60  
  Purchase #4 $108.40   10.413%   $119.6877   $119.69   $119.70   $119.70  
  Purchase #5 $76.28   3.559%   $78.9948   $78.99   $79.00   $79.00  
  Purchase #6 $64.42   12.162%   $72.2548   $72.25   $72.25   $72.30  
  Purchase #7 $220.25   7.726%   $237.2665   $237.27   $237.25   $237.30  
  7 purchase totals = $894.21       $959.4870   $959.49   $959.50   $959.50