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 $214.31   10.699%   $237.239   $237.24   $237.25   $237.20  
  Purchase #2 $210.39   3.434%   $217.6148   $217.61   $217.60   $217.60  
  Purchase #3 $115.67   10.564%   $127.8894   $127.89   $127.90   $127.90  
  Purchase #4 $175.46   4.450%   $183.268   $183.27   $183.25   $183.30  
  Purchase #5 $160.29   9.861%   $176.0962   $176.10   $176.10   $176.10  
  Purchase #6 $170.32   12.835%   $192.1806   $192.18   $192.20   $192.20  
  Purchase #7 $104.40   12.465%   $117.4135   $117.41   $117.40   $117.40  
  7 purchase totals = $1,150.84       $1,251.7015   $1,251.70   $1,251.70   $1,251.70