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 $61.67   10.817%   $68.3408   $68.34   $68.35   $68.30  
  Purchase #2 $224.96   12.752%   $253.6469   $253.65   $253.65   $253.60  
  Purchase #3 $101.69   12.871%   $114.7785   $114.78   $114.80   $114.80  
  Purchase #4 $235.31   5.453%   $248.1415   $248.14   $248.15   $248.10  
  Purchase #5 $172.58   9.734%   $189.3789   $189.38   $189.40   $189.40  
  Purchase #6 $96.80   8.293%   $104.8276   $104.83   $104.85   $104.80  
  Purchase #7 $139.28   6.285%   $148.0337   $148.03   $148.05   $148.00  
  7 purchase totals = $1,032.29       $1,127.1479   $1,127.15   $1,127.25   $1,127.00