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 $106.91   7.524%   $114.9539   $114.95   $114.95   $115.00  
  Purchase #2 $114.96   9.568%   $125.9594   $125.96   $125.95   $126.00  
  Purchase #3 $49.96   6.789%   $53.3518   $53.35   $53.35   $53.40  
  Purchase #4 $49.48   5.649%   $52.2751   $52.28   $52.30   $52.30  
  Purchase #5 $222.68   4.874%   $233.5334   $233.53   $233.55   $233.50  
  Purchase #6 $169.71   8.738%   $184.5393   $184.54   $184.55   $184.50  
  Purchase #7 $232.95   4.104%   $242.5103   $242.51   $242.50   $242.50  
  7 purchase totals = $946.65       $1,007.1232   $1,007.12   $1,007.15   $1,007.20