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 $116.65   7.548%   $125.4547   $125.45   $125.45   $125.50  
  Purchase #2 $208.66   13.511%   $236.8521   $236.85   $236.85   $236.90  
  Purchase #3 $96.91   10.178%   $106.7735   $106.77   $106.75   $106.80  
  Purchase #4 $227.95   10.313%   $251.4585   $251.46   $251.45   $251.50  
  Purchase #5 $139.68   4.296%   $145.6807   $145.68   $145.70   $145.70  
  Purchase #6 $178.94   8.195%   $193.6041   $193.60   $193.60   $193.60  
  Purchase #7 $236.92   10.730%   $262.3415   $262.34   $262.35   $262.30  
  7 purchase totals = $1,205.71       $1,322.1651   $1,322.15   $1,322.15   $1,322.30