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 $194.91   3.122%   $200.9951   $201.00   $201.00   $201.00  
  Purchase #2 $233.87   6.278%   $248.5524   $248.55   $248.55   $248.60  
  Purchase #3 $86.60   6.549%   $92.2714   $92.27   $92.25   $92.30  
  Purchase #4 $5.60   9.823%   $6.1501   $6.15   $6.15   $6.20  
  Purchase #5 $229.33   3.311%   $236.9231   $236.92   $236.90   $236.90  
  Purchase #6 $197.66   6.577%   $210.6601   $210.66   $210.65   $210.70  
  Purchase #7 $250.36   10.456%   $276.5376   $276.54   $276.55   $276.50  
  7 purchase totals = $1,198.33       $1,272.0898   $1,272.09   $1,272.05   $1,272.20