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 $214.83   9.809%   $235.9027   $235.90   $235.90   $235.90  
  Purchase #2 $67.75   9.156%   $73.9532   $73.95   $73.95   $74.00  
  Purchase #3 $81.36   9.684%   $89.2389   $89.24   $89.25   $89.20  
  Purchase #4 $198.63   3.105%   $204.7975   $204.80   $204.80   $204.80  
  Purchase #5 $105.63   4.636%   $110.527   $110.53   $110.55   $110.50  
  Purchase #6 $147.78   10.874%   $163.8496   $163.85   $163.85   $163.80  
  Purchase #7 $125.88   12.240%   $141.2877   $141.29   $141.30   $141.30  
  7 purchase totals = $941.86       $1,019.5566   $1,019.56   $1,019.60   $1,019.50