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 $39.94   11.262%   $44.438   $44.44   $44.45   $44.40  
  Purchase #2 $47.72   3.617%   $49.446   $49.45   $49.45   $49.40  
  Purchase #3 $173.40   3.739%   $179.8834   $179.88   $179.90   $179.90  
  Purchase #4 $145.60   8.470%   $157.9323   $157.93   $157.95   $157.90  
  Purchase #5 $111.31   11.395%   $123.9938   $123.99   $124.00   $124.00  
  Purchase #6 $58.87   13.291%   $66.6944   $66.69   $66.70   $66.70  
  Purchase #7 $126.94   4.726%   $132.9392   $132.94   $132.95   $132.90  
  7 purchase totals = $703.78       $755.3271   $755.32   $755.40   $755.20