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 $213.27   11.247%   $237.2565   $237.26   $237.25   $237.30  
  Purchase #2 $56.84   10.429%   $62.7678   $62.77   $62.75   $62.80  
  Purchase #3 $71.73   13.274%   $81.2514   $81.25   $81.25   $81.30  
  Purchase #4 $21.81   5.381%   $22.9836   $22.98   $23.00   $23.00  
  Purchase #5 $120.55   6.686%   $128.61   $128.61   $128.60   $128.60  
  Purchase #6 $237.87   5.213%   $250.2702   $250.27   $250.25   $250.30  
  Purchase #7 $176.60   4.308%   $184.2079   $184.21   $184.20   $184.20  
  7 purchase totals = $898.67       $967.3474   $967.35   $967.30   $967.50