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 $24.48   7.347%   $26.2785   $26.28   $26.30   $26.30  
  Purchase #2 $113.79   6.451%   $121.1306   $121.13   $121.15   $121.10  
  Purchase #3 $100.55   13.702%   $114.3274   $114.33   $114.35   $114.30  
  Purchase #4 $158.84   9.516%   $173.9552   $173.96   $173.95   $174.00  
  Purchase #5 $157.54   12.495%   $177.2246   $177.22   $177.20   $177.20  
  Purchase #6 $198.76   3.537%   $205.7901   $205.79   $205.80   $205.80  
  Purchase #7 $72.43   5.368%   $76.318   $76.32   $76.30   $76.30  
  7 purchase totals = $826.39       $895.0244   $895.03   $895.05   $895.00