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 $114.69   3.544%   $118.7546   $118.75   $118.75   $118.80  
  Purchase #2 $168.60   4.814%   $176.7164   $176.72   $176.70   $176.70  
  Purchase #3 $53.46   7.502%   $57.4706   $57.47   $57.45   $57.50  
  Purchase #4 $105.37   8.603%   $114.435   $114.44   $114.45   $114.40  
  Purchase #5 $202.58   8.872%   $220.5529   $220.55   $220.55   $220.60  
  Purchase #6 $183.90   6.643%   $196.1165   $196.12   $196.10   $196.10  
  Purchase #7 $179.43   8.472%   $194.6313   $194.63   $194.65   $194.60  
  7 purchase totals = $1,008.03       $1,078.6773   $1,078.68   $1,078.65   $1,078.70