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 $57.38   7.700%   $61.7983   $61.80   $61.80   $61.80  
  Purchase #2 $119.63   6.827%   $127.7971   $127.80   $127.80   $127.80  
  Purchase #3 $20.93   10.738%   $23.1775   $23.18   $23.20   $23.20  
  Purchase #4 $181.54   11.119%   $201.7254   $201.73   $201.75   $201.70  
  Purchase #5 $206.95   3.849%   $214.9155   $214.92   $214.90   $214.90  
  Purchase #6 $182.83   12.217%   $205.1663   $205.17   $205.15   $205.20  
  Purchase #7 $207.64   8.115%   $224.49   $224.49   $224.50   $224.50  
  7 purchase totals = $976.90       $1,059.0701   $1,059.09   $1,059.10   $1,059.10