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 $95.86   4.513%   $100.1862   $100.19   $100.20   $100.20  
  Purchase #2 $63.62   7.191%   $68.1949   $68.19   $68.20   $68.20  
  Purchase #3 $104.50   9.734%   $114.672   $114.67   $114.65   $114.70  
  Purchase #4 $208.70   7.547%   $224.4506   $224.45   $224.45   $224.50  
  Purchase #5 $248.96   6.632%   $265.471   $265.47   $265.45   $265.50  
  Purchase #6 $103.65   12.444%   $116.5482   $116.55   $116.55   $116.50  
  Purchase #7 $171.58   3.369%   $177.3605   $177.36   $177.35   $177.40  
  7 purchase totals = $996.87       $1,066.8834   $1,066.88   $1,066.85   $1,067.00