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 $237.41   5.105%   $249.5298   $249.53   $249.55   $249.50  
  Purchase #2 $198.26   3.626%   $205.4489   $205.45   $205.45   $205.40  
  Purchase #3 $61.72   7.227%   $66.1805   $66.18   $66.20   $66.20  
  Purchase #4 $187.42   10.617%   $207.3184   $207.32   $207.30   $207.30  
  Purchase #5 $13.37   6.619%   $14.255   $14.26   $14.25   $14.30  
  Purchase #6 $147.57   7.748%   $159.0037   $159.00   $159.00   $159.00  
  Purchase #7 $202.30   7.412%   $217.2945   $217.29   $217.30   $217.30  
  7 purchase totals = $1,048.05       $1,119.0308   $1,119.03   $1,119.05   $1,119.00