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 $130.40   9.548%   $142.8506   $142.85   $142.85   $142.90  
  Purchase #2 $232.42   13.252%   $263.2203   $263.22   $263.20   $263.20  
  Purchase #3 $183.34   3.871%   $190.4371   $190.44   $190.45   $190.40  
  Purchase #4 $60.51   6.506%   $64.4468   $64.45   $64.45   $64.40  
  Purchase #5 $212.82   9.206%   $232.4122   $232.41   $232.40   $232.40  
  Purchase #6 $76.61   6.125%   $81.3024   $81.30   $81.30   $81.30  
  Purchase #7 $60.67   9.611%   $66.501   $66.50   $66.50   $66.50  
  7 purchase totals = $956.77       $1,041.1704   $1,041.17   $1,041.15   $1,041.10