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 $22.51   9.674%   $24.6876   $24.69   $24.70   $24.70  
  Purchase #2 $240.38   11.398%   $267.7785   $267.78   $267.80   $267.80  
  Purchase #3 $95.61   9.109%   $104.3191   $104.32   $104.30   $104.30  
  Purchase #4 $202.57   5.872%   $214.4649   $214.46   $214.45   $214.50  
  Purchase #5 $193.45   10.410%   $213.5881   $213.59   $213.60   $213.60  
  Purchase #6 $177.58   4.178%   $184.9993   $185.00   $185.00   $185.00  
  Purchase #7 $174.87   9.311%   $191.1521   $191.15   $191.15   $191.20  
  7 purchase totals = $1,106.97       $1,200.9896   $1,200.99   $1,201.00   $1,201.10