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 $94.68   11.174%   $105.2595   $105.26   $105.25   $105.30  
  Purchase #2 $176.57   10.614%   $195.3111   $195.31   $195.30   $195.30  
  Purchase #3 $130.59   3.227%   $134.8041   $134.80   $134.80   $134.80  
  Purchase #4 $164.38   7.792%   $177.1885   $177.19   $177.20   $177.20  
  Purchase #5 $73.64   11.815%   $82.3406   $82.34   $82.35   $82.30  
  Purchase #6 $100.28   5.539%   $105.8345   $105.83   $105.85   $105.80  
  Purchase #7 $240.78   4.663%   $252.0076   $252.01   $252.00   $252.00  
  7 purchase totals = $980.92       $1,052.7459   $1,052.74   $1,052.75   $1,052.70