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 $193.51   3.379%   $200.0487   $200.05   $200.05   $200.00  
  Purchase #2 $44.76   4.587%   $46.8131   $46.81   $46.80   $46.80  
  Purchase #3 $111.49   5.794%   $117.9497   $117.95   $117.95   $117.90  
  Purchase #4 $92.40   9.668%   $101.3332   $101.33   $101.35   $101.30  
  Purchase #5 $153.80   3.565%   $159.283   $159.28   $159.30   $159.30  
  Purchase #6 $14.29   3.556%   $14.7982   $14.80   $14.80   $14.80  
  Purchase #7 $233.98   7.712%   $252.0245   $252.02   $252.00   $252.00  
  7 purchase totals = $844.23       $892.2504   $892.24   $892.25   $892.10