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 $92.69   13.297%   $105.015   $105.02   $105.00   $105.00  
  Purchase #2 $32.27   13.422%   $36.6013   $36.60   $36.60   $36.60  
  Purchase #3 $248.63   10.771%   $275.4099   $275.41   $275.40   $275.40  
  Purchase #4 $135.26   9.306%   $147.8473   $147.85   $147.85   $147.80  
  Purchase #5 $127.31   6.746%   $135.8983   $135.90   $135.90   $135.90  
  Purchase #6 $242.32   3.211%   $250.1009   $250.10   $250.10   $250.10  
  Purchase #7 $155.78   4.255%   $162.4084   $162.41   $162.40   $162.40  
  7 purchase totals = $1,034.26       $1,113.2811   $1,113.29   $1,113.25   $1,113.20