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 $83.41   13.803%   $94.9231   $94.92   $94.90   $94.90  
  Purchase #2 $30.83   3.393%   $31.8761   $31.88   $31.90   $31.90  
  Purchase #3 $72.66   4.138%   $75.6667   $75.67   $75.65   $75.70  
  Purchase #4 $191.39   11.852%   $214.0735   $214.07   $214.05   $214.10  
  Purchase #5 $208.27   8.296%   $225.5481   $225.55   $225.55   $225.50  
  Purchase #6 $174.63   13.815%   $198.7551   $198.76   $198.75   $198.80  
  Purchase #7 $192.41   4.139%   $200.3738   $200.37   $200.35   $200.40  
  7 purchase totals = $953.60       $1,041.2164   $1,041.22   $1,041.15   $1,041.30