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 $114.96   10.295%   $126.7951   $126.80   $126.80   $126.80  
  Purchase #2 $141.40   12.723%   $159.3903   $159.39   $159.40   $159.40  
  Purchase #3 $239.67   9.312%   $261.9881   $261.99   $262.00   $262.00  
  Purchase #4 $189.69   8.589%   $205.9825   $205.98   $206.00   $206.00  
  Purchase #5 $232.82   3.617%   $241.2411   $241.24   $241.25   $241.20  
  Purchase #6 $11.26   9.858%   $12.37   $12.37   $12.35   $12.40  
  Purchase #7 $14.59   3.701%   $15.13   $15.13   $15.15   $15.10  
  7 purchase totals = $944.39       $1,022.8971   $1,022.90   $1,022.95   $1,022.90