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 $195.45   6.551%   $208.2539   $208.25   $208.25   $208.30  
  Purchase #2 $242.92   10.829%   $269.2258   $269.23   $269.25   $269.20  
  Purchase #3 $108.34   8.156%   $117.1762   $117.18   $117.20   $117.20  
  Purchase #4 $35.30   7.839%   $38.0672   $38.07   $38.05   $38.10  
  Purchase #5 $204.63   5.485%   $215.854   $215.85   $215.85   $215.90  
  Purchase #6 $150.33   8.824%   $163.5951   $163.60   $163.60   $163.60  
  Purchase #7 $57.49   5.619%   $60.7204   $60.72   $60.70   $60.70  
  7 purchase totals = $994.46       $1,072.8926   $1,072.90   $1,072.90   $1,073.00