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 $202.49   5.705%   $214.0421   $214.04   $214.05   $214.00  
  Purchase #2 $158.32   6.538%   $168.671   $168.67   $168.65   $168.70  
  Purchase #3 $151.46   3.519%   $156.7899   $156.79   $156.80   $156.80  
  Purchase #4 $88.66   9.588%   $97.1607   $97.16   $97.15   $97.20  
  Purchase #5 $82.69   9.254%   $90.3421   $90.34   $90.35   $90.30  
  Purchase #6 $209.70   7.486%   $225.3981   $225.40   $225.40   $225.40  
  Purchase #7 $59.93   7.396%   $64.3624   $64.36   $64.35   $64.40  
  7 purchase totals = $953.25       $1,016.7663   $1,016.76   $1,016.75   $1,016.80