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 $245.95   6.303%   $261.4522   $261.45   $261.45   $261.50  
  Purchase #2 $198.61   6.313%   $211.1482   $211.15   $211.15   $211.10  
  Purchase #3 $37.28   9.497%   $40.8205   $40.82   $40.80   $40.80  
  Purchase #4 $233.69   10.533%   $258.3046   $258.30   $258.30   $258.30  
  Purchase #5 $173.53   13.730%   $197.3557   $197.36   $197.35   $197.40  
  Purchase #6 $222.28   3.171%   $229.3285   $229.33   $229.35   $229.30  
  Purchase #7 $184.99   11.333%   $205.9549   $205.95   $205.95   $206.00  
  7 purchase totals = $1,296.33       $1,404.3646   $1,404.36   $1,404.35   $1,404.40