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 $214.36   10.192%   $236.2076   $236.21   $236.20   $236.20  
  Purchase #2 $149.51   12.195%   $167.7427   $167.74   $167.75   $167.70  
  Purchase #3 $72.46   7.248%   $77.7119   $77.71   $77.70   $77.70  
  Purchase #4 $244.83   4.826%   $256.6455   $256.65   $256.65   $256.60  
  Purchase #5 $13.63   4.597%   $14.2566   $14.26   $14.25   $14.30  
  Purchase #6 $196.42   5.680%   $207.5767   $207.58   $207.60   $207.60  
  Purchase #7 $215.26   9.661%   $236.0563   $236.06   $236.05   $236.10  
  7 purchase totals = $1,106.47       $1,196.1973   $1,196.21   $1,196.20   $1,196.20