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 $184.34   4.837%   $193.2565   $193.26   $193.25   $193.30  
  Purchase #2 $213.78   10.492%   $236.2098   $236.21   $236.20   $236.20  
  Purchase #3 $226.87   7.728%   $244.4025   $244.40   $244.40   $244.40  
  Purchase #4 $208.34   3.326%   $215.2694   $215.27   $215.25   $215.30  
  Purchase #5 $206.65   11.523%   $230.4623   $230.46   $230.45   $230.50  
  Purchase #6 $59.83   8.413%   $64.8635   $64.86   $64.85   $64.90  
  Purchase #7 $186.95   4.811%   $195.9442   $195.94   $195.95   $195.90  
  7 purchase totals = $1,286.76       $1,380.4082   $1,380.40   $1,380.35   $1,380.50