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 $166.45   10.828%   $184.4732   $184.47   $184.45   $184.50  
  Purchase #2 $227.76   3.337%   $235.3604   $235.36   $235.35   $235.40  
  Purchase #3 $14.91   10.497%   $16.4751   $16.48   $16.50   $16.50  
  Purchase #4 $112.46   8.543%   $122.0675   $122.07   $122.05   $122.10  
  Purchase #5 $218.64   4.102%   $227.6086   $227.61   $227.60   $227.60  
  Purchase #6 $198.63   3.451%   $205.4847   $205.48   $205.50   $205.50  
  Purchase #7 $125.80   7.222%   $134.8853   $134.89   $134.90   $134.90  
  7 purchase totals = $1,064.65       $1,126.3548   $1,126.36   $1,126.35   $1,126.50