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 $178.71   13.152%   $202.2139   $202.21   $202.20   $202.20  
  Purchase #2 $241.60   8.511%   $262.1626   $262.16   $262.15   $262.20  
  Purchase #3 $157.40   8.410%   $170.6373   $170.64   $170.65   $170.60  
  Purchase #4 $64.90   12.462%   $72.9878   $72.99   $73.00   $73.00  
  Purchase #5 $125.88   11.757%   $140.6797   $140.68   $140.70   $140.70  
  Purchase #6 $207.80   9.256%   $227.034   $227.03   $227.05   $227.00  
  Purchase #7 $77.32   5.544%   $81.6066   $81.61   $81.60   $81.60  
  7 purchase totals = $1,053.61       $1,157.3219   $1,157.32   $1,157.35   $1,157.30