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 $181.61   5.717%   $191.9926   $191.99   $192.00   $192.00  
  Purchase #2 $74.73   8.710%   $81.239   $81.24   $81.25   $81.20  
  Purchase #3 $11.53   4.296%   $12.0253   $12.03   $12.05   $12.00  
  Purchase #4 $11.97   12.687%   $13.4886   $13.49   $13.50   $13.50  
  Purchase #5 $75.27   4.413%   $78.5917   $78.59   $78.60   $78.60  
  Purchase #6 $119.26   6.224%   $126.6827   $126.68   $126.70   $126.70  
  Purchase #7 $239.77   5.313%   $252.509   $252.51   $252.50   $252.50  
  7 purchase totals = $714.14       $756.5289   $756.53   $756.60   $756.50