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 $64.71   4.542%   $67.6491   $67.65   $67.65   $67.60  
  Purchase #2 $214.92   10.431%   $237.3383   $237.34   $237.35   $237.30  
  Purchase #3 $154.77   3.611%   $160.3587   $160.36   $160.35   $160.40  
  Purchase #4 $228.37   3.663%   $236.7352   $236.74   $236.75   $236.70  
  Purchase #5 $103.86   9.852%   $114.0923   $114.09   $114.10   $114.10  
  Purchase #6 $201.75   7.282%   $216.4414   $216.44   $216.45   $216.40  
  Purchase #7 $74.53   4.335%   $77.7609   $77.76   $77.75   $77.80  
  7 purchase totals = $1,042.91       $1,110.3759   $1,110.38   $1,110.40   $1,110.30