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 $241.77   7.818%   $260.6716   $260.67   $260.65   $260.70  
  Purchase #2 $19.48   3.700%   $20.2008   $20.20   $20.20   $20.20  
  Purchase #3 $157.63   9.428%   $172.4914   $172.49   $172.50   $172.50  
  Purchase #4 $12.91   9.159%   $14.0924   $14.09   $14.10   $14.10  
  Purchase #5 $156.88   9.433%   $171.6785   $171.68   $171.70   $171.70  
  Purchase #6 $175.92   13.132%   $199.0218   $199.02   $199.00   $199.00  
  Purchase #7 $170.34   3.467%   $176.2457   $176.25   $176.25   $176.20  
  7 purchase totals = $934.93       $1,014.4022   $1,014.40   $1,014.40   $1,014.40