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 $180.26   8.523%   $195.6236   $195.62   $195.60   $195.60  
  Purchase #2 $209.48   10.845%   $232.1981   $232.20   $232.20   $232.20  
  Purchase #3 $82.94   11.266%   $92.284   $92.28   $92.30   $92.30  
  Purchase #4 $43.35   3.674%   $44.9427   $44.94   $44.95   $44.90  
  Purchase #5 $94.66   4.236%   $98.6698   $98.67   $98.65   $98.70  
  Purchase #6 $11.49   3.838%   $11.931   $11.93   $11.95   $11.90  
  Purchase #7 $215.49   4.403%   $224.978   $224.98   $225.00   $225.00  
  7 purchase totals = $837.67       $900.6272   $900.62   $900.65   $900.60