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 $195.67   13.805%   $222.6822   $222.68   $222.70   $222.70  
  Purchase #2 $89.72   9.541%   $98.2802   $98.28   $98.30   $98.30  
  Purchase #3 $224.55   3.325%   $232.0163   $232.02   $232.00   $232.00  
  Purchase #4 $175.58   13.370%   $199.055   $199.06   $199.05   $199.10  
  Purchase #5 $192.29   7.260%   $206.2503   $206.25   $206.25   $206.30  
  Purchase #6 $63.83   4.440%   $66.6641   $66.66   $66.65   $66.70  
  Purchase #7 $181.71   10.814%   $201.3601   $201.36   $201.35   $201.40  
  7 purchase totals = $1,123.35       $1,226.3082   $1,226.31   $1,226.30   $1,226.50