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 $60.90   13.366%   $69.0399   $69.04   $69.05   $69.00  
  Purchase #2 $235.59   6.810%   $251.6337   $251.63   $251.65   $251.60  
  Purchase #3 $185.58   9.230%   $202.709   $202.71   $202.70   $202.70  
  Purchase #4 $218.40   3.859%   $226.8281   $226.83   $226.85   $226.80  
  Purchase #5 $126.66   12.665%   $142.7015   $142.70   $142.70   $142.70  
  Purchase #6 $206.47   12.306%   $231.8782   $231.88   $231.90   $231.90  
  Purchase #7 $192.34   4.105%   $200.2356   $200.24   $200.25   $200.20  
  7 purchase totals = $1,225.94       $1,325.0260   $1,325.03   $1,325.10   $1,324.90