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 $214.25   10.362%   $236.4506   $236.45   $236.45   $236.50  
  Purchase #2 $59.36   5.379%   $62.553   $62.55   $62.55   $62.60  
  Purchase #3 $250.97   7.465%   $269.7049   $269.70   $269.70   $269.70  
  Purchase #4 $102.80   3.122%   $106.0094   $106.01   $106.00   $106.00  
  Purchase #5 $176.68   9.501%   $193.4664   $193.47   $193.45   $193.50  
  Purchase #6 $20.77   12.831%   $23.435   $23.44   $23.45   $23.40  
  Purchase #7 $249.60   13.583%   $283.5032   $283.50   $283.50   $283.50  
  7 purchase totals = $1,074.43       $1,175.1225   $1,175.12   $1,175.10   $1,175.20