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 $114.32   3.821%   $118.6882   $118.69   $118.70   $118.70  
  Purchase #2 $232.88   9.491%   $254.9826   $254.98   $255.00   $255.00  
  Purchase #3 $199.88   8.407%   $216.6839   $216.68   $216.70   $216.70  
  Purchase #4 $144.35   8.599%   $156.7627   $156.76   $156.75   $156.80  
  Purchase #5 $102.32   6.122%   $108.584   $108.58   $108.60   $108.60  
  Purchase #6 $80.93   8.822%   $88.0696   $88.07   $88.05   $88.10  
  Purchase #7 $198.95   5.704%   $210.2981   $210.30   $210.30   $210.30  
  7 purchase totals = $1,073.63       $1,154.0691   $1,154.06   $1,154.10   $1,154.20