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 $87.59   9.270%   $95.7096   $95.71   $95.70   $95.70  
  Purchase #2 $27.35   3.749%   $28.3754   $28.38   $28.40   $28.40  
  Purchase #3 $205.83   5.764%   $217.694   $217.69   $217.70   $217.70  
  Purchase #4 $214.61   8.866%   $233.6373   $233.64   $233.65   $233.60  
  Purchase #5 $208.42   13.319%   $236.1795   $236.18   $236.20   $236.20  
  Purchase #6 $206.63   8.694%   $224.5944   $224.59   $224.60   $224.60  
  Purchase #7 $49.46   12.846%   $55.8136   $55.81   $55.80   $55.80  
  7 purchase totals = $999.89       $1,092.0038   $1,092.00   $1,092.05   $1,092.00