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 $84.88   11.451%   $94.5996   $94.60   $94.60   $94.60  
  Purchase #2 $22.91   3.312%   $23.6688   $23.67   $23.65   $23.70  
  Purchase #3 $144.51   13.854%   $164.5304   $164.53   $164.55   $164.50  
  Purchase #4 $224.35   6.705%   $239.3927   $239.39   $239.40   $239.40  
  Purchase #5 $69.32   4.684%   $72.5669   $72.57   $72.55   $72.60  
  Purchase #6 $166.98   10.358%   $184.2758   $184.28   $184.30   $184.30  
  Purchase #7 $77.88   13.468%   $88.3689   $88.37   $88.35   $88.40  
  7 purchase totals = $790.83       $867.4031   $867.41   $867.40   $867.50