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 $181.68   7.296%   $194.9354   $194.94   $194.95   $194.90  
  Purchase #2 $105.40   9.545%   $115.4604   $115.46   $115.45   $115.50  
  Purchase #3 $163.95   8.287%   $177.5365   $177.54   $177.55   $177.50  
  Purchase #4 $68.77   5.655%   $72.6589   $72.66   $72.65   $72.70  
  Purchase #5 $217.44   8.125%   $235.107   $235.11   $235.10   $235.10  
  Purchase #6 $172.32   7.550%   $185.3302   $185.33   $185.35   $185.30  
  Purchase #7 $250.40   7.642%   $269.5356   $269.54   $269.55   $269.50  
  7 purchase totals = $1,159.96       $1,250.5640   $1,250.58   $1,250.60   $1,250.50