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 $59.26   3.823%   $61.5255   $61.53   $61.55   $61.50  
  Purchase #2 $98.66   6.225%   $104.8016   $104.80   $104.80   $104.80  
  Purchase #3 $99.69   7.564%   $107.2306   $107.23   $107.25   $107.20  
  Purchase #4 $32.84   4.646%   $34.3657   $34.37   $34.35   $34.40  
  Purchase #5 $163.76   12.756%   $184.6492   $184.65   $184.65   $184.60  
  Purchase #6 $12.43   10.771%   $13.7688   $13.77   $13.75   $13.80  
  Purchase #7 $207.41   9.513%   $227.1409   $227.14   $227.15   $227.10  
  7 purchase totals = $674.05       $733.4823   $733.49   $733.50   $733.40