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 $108.96   9.230%   $119.017   $119.02   $119.00   $119.00  
  Purchase #2 $204.78   6.268%   $217.6156   $217.62   $217.60   $217.60  
  Purchase #3 $222.67   8.839%   $242.3518   $242.35   $242.35   $242.40  
  Purchase #4 $197.25   11.217%   $219.3755   $219.38   $219.40   $219.40  
  Purchase #5 $219.71   7.455%   $236.0894   $236.09   $236.10   $236.10  
  Purchase #6 $238.40   9.494%   $261.0337   $261.03   $261.05   $261.00  
  Purchase #7 $227.59   9.426%   $249.0426   $249.04   $249.05   $249.00  
  7 purchase totals = $1,419.36       $1,544.5256   $1,544.53   $1,544.55   $1,544.50