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 $195.69   6.429%   $208.2709   $208.27   $208.25   $208.30  
  Purchase #2 $10.74   13.441%   $12.1836   $12.18   $12.20   $12.20  
  Purchase #3 $114.91   5.323%   $121.0267   $121.03   $121.05   $121.00  
  Purchase #4 $166.37   4.367%   $173.6354   $173.64   $173.65   $173.60  
  Purchase #5 $192.66   3.296%   $199.0101   $199.01   $199.00   $199.00  
  Purchase #6 $159.34   8.314%   $172.5875   $172.59   $172.60   $172.60  
  Purchase #7 $248.44   7.705%   $267.5823   $267.58   $267.60   $267.60  
  7 purchase totals = $1,088.15       $1,154.2965   $1,154.30   $1,154.35   $1,154.30