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 $92.82   3.152%   $95.7457   $95.75   $95.75   $95.70  
  Purchase #2 $224.44   6.794%   $239.6885   $239.69   $239.70   $239.70  
  Purchase #3 $184.87   4.276%   $192.775   $192.78   $192.80   $192.80  
  Purchase #4 $187.97   9.738%   $206.2745   $206.27   $206.25   $206.30  
  Purchase #5 $128.38   8.330%   $139.0741   $139.07   $139.05   $139.10  
  Purchase #6 $84.63   6.867%   $90.4415   $90.44   $90.45   $90.40  
  Purchase #7 $83.71   6.808%   $89.409   $89.41   $89.40   $89.40  
  7 purchase totals = $986.82       $1,053.4083   $1,053.41   $1,053.40   $1,053.40