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 $187.53   9.763%   $205.8386   $205.84   $205.85   $205.80  
  Purchase #2 $69.82   6.344%   $74.2494   $74.25   $74.25   $74.20  
  Purchase #3 $222.28   9.143%   $242.6031   $242.60   $242.60   $242.60  
  Purchase #4 $93.45   5.164%   $98.2758   $98.28   $98.30   $98.30  
  Purchase #5 $109.30   4.636%   $114.3671   $114.37   $114.35   $114.40  
  Purchase #6 $200.91   10.538%   $222.0819   $222.08   $222.10   $222.10  
  Purchase #7 $49.74   7.433%   $53.4372   $53.44   $53.45   $53.40  
  7 purchase totals = $933.03       $1,010.8531   $1,010.86   $1,010.90   $1,010.80