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 $58.61   8.705%   $63.712   $63.71   $63.70   $63.70  
  Purchase #2 $234.82   3.139%   $242.191   $242.19   $242.20   $242.20  
  Purchase #3 $44.49   5.256%   $46.8284   $46.83   $46.85   $46.80  
  Purchase #4 $33.46   4.221%   $34.8723   $34.87   $34.85   $34.90  
  Purchase #5 $195.28   9.207%   $213.2594   $213.26   $213.25   $213.30  
  Purchase #6 $53.30   7.135%   $57.103   $57.10   $57.10   $57.10  
  Purchase #7 $185.81   9.420%   $203.3133   $203.31   $203.30   $203.30  
  7 purchase totals = $805.77       $861.2794   $861.27   $861.25   $861.30