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 $65.85   5.716%   $69.614   $69.61   $69.60   $69.60  
  Purchase #2 $28.89   5.313%   $30.4249   $30.42   $30.40   $30.40  
  Purchase #3 $160.55   11.259%   $178.6263   $178.63   $178.65   $178.60  
  Purchase #4 $203.91   6.517%   $217.1988   $217.20   $217.20   $217.20  
  Purchase #5 $202.64   12.486%   $227.9416   $227.94   $227.95   $227.90  
  Purchase #6 $226.45   9.459%   $247.8699   $247.87   $247.85   $247.90  
  Purchase #7 $206.83   3.665%   $214.4103   $214.41   $214.40   $214.40  
  7 purchase totals = $1,095.12       $1,186.0858   $1,186.08   $1,186.05   $1,186.00