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 $208.60   11.218%   $232.0007   $232.00   $232.00   $232.00  
  Purchase #2 $183.98   7.617%   $197.9938   $197.99   $198.00   $198.00  
  Purchase #3 $155.68   7.291%   $167.0306   $167.03   $167.05   $167.00  
  Purchase #4 $45.65   8.493%   $49.5271   $49.53   $49.55   $49.50  
  Purchase #5 $17.95   11.161%   $19.9534   $19.95   $19.95   $20.00  
  Purchase #6 $204.45   13.471%   $231.9915   $231.99   $232.00   $232.00  
  Purchase #7 $247.68   11.457%   $276.0567   $276.06   $276.05   $276.10  
  7 purchase totals = $1,063.99       $1,174.5538   $1,174.55   $1,174.60   $1,174.60