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 $62.39   11.325%   $69.4557   $69.46   $69.45   $69.50  
  Purchase #2 $15.61   10.492%   $17.2478   $17.25   $17.25   $17.20  
  Purchase #3 $224.91   10.856%   $249.3262   $249.33   $249.35   $249.30  
  Purchase #4 $208.43   4.759%   $218.3492   $218.35   $218.35   $218.30  
  Purchase #5 $233.84   3.688%   $242.464   $242.46   $242.45   $242.50  
  Purchase #6 $185.94   8.296%   $201.3656   $201.37   $201.35   $201.40  
  Purchase #7 $89.85   7.262%   $96.3749   $96.37   $96.35   $96.40  
  7 purchase totals = $1,020.97       $1,094.5834   $1,094.59   $1,094.55   $1,094.60