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 $176.29   11.586%   $196.715   $196.72   $196.70   $196.70  
  Purchase #2 $220.88   12.437%   $248.3508   $248.35   $248.35   $248.40  
  Purchase #3 $49.71   8.509%   $53.9398   $53.94   $53.95   $53.90  
  Purchase #4 $165.48   10.825%   $183.3932   $183.39   $183.40   $183.40  
  Purchase #5 $164.32   3.241%   $169.6456   $169.65   $169.65   $169.60  
  Purchase #6 $121.33   11.508%   $135.2927   $135.29   $135.30   $135.30  
  Purchase #7 $226.96   5.591%   $239.6493   $239.65   $239.65   $239.60  
  7 purchase totals = $1,124.97       $1,226.9864   $1,226.99   $1,227.00   $1,226.90