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 $223.28   4.662%   $233.6893   $233.69   $233.70   $233.70  
  Purchase #2 $187.30   3.657%   $194.1496   $194.15   $194.15   $194.10  
  Purchase #3 $212.80   6.308%   $226.2234   $226.22   $226.20   $226.20  
  Purchase #4 $77.36   6.621%   $82.482   $82.48   $82.50   $82.50  
  Purchase #5 $182.63   7.325%   $196.0076   $196.01   $196.00   $196.00  
  Purchase #6 $203.36   12.724%   $229.2355   $229.24   $229.25   $229.20  
  Purchase #7 $70.44   7.867%   $75.9815   $75.98   $76.00   $76.00  
  7 purchase totals = $1,157.17       $1,237.7689   $1,237.77   $1,237.80   $1,237.70