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 $206.52   3.425%   $213.5933   $213.59   $213.60   $213.60  
  Purchase #2 $50.68   10.592%   $56.048   $56.05   $56.05   $56.00  
  Purchase #3 $37.92   6.717%   $40.4671   $40.47   $40.45   $40.50  
  Purchase #4 $73.83   3.734%   $76.5868   $76.59   $76.60   $76.60  
  Purchase #5 $80.39   3.457%   $83.1691   $83.17   $83.15   $83.20  
  Purchase #6 $200.70   5.104%   $210.9437   $210.94   $210.95   $210.90  
  Purchase #7 $184.63   5.874%   $195.4752   $195.48   $195.50   $195.50  
  7 purchase totals = $834.67       $876.2832   $876.29   $876.30   $876.30