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 $88.30   8.577%   $95.8735   $95.87   $95.85   $95.90  
  Purchase #2 $187.40   3.129%   $193.2637   $193.26   $193.25   $193.30  
  Purchase #3 $117.25   7.789%   $126.3826   $126.38   $126.40   $126.40  
  Purchase #4 $116.96   8.839%   $127.2981   $127.30   $127.30   $127.30  
  Purchase #5 $136.35   12.781%   $153.7769   $153.78   $153.80   $153.80  
  Purchase #6 $226.91   9.615%   $248.7274   $248.73   $248.75   $248.70  
  Purchase #7 $170.71   3.791%   $177.1816   $177.18   $177.20   $177.20  
  7 purchase totals = $1,043.88       $1,122.5038   $1,122.50   $1,122.55   $1,122.60