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 $118.34   5.182%   $124.4724   $124.47   $124.45   $124.50  
  Purchase #2 $201.42   4.855%   $211.1989   $211.20   $211.20   $211.20  
  Purchase #3 $232.64   5.365%   $245.1211   $245.12   $245.10   $245.10  
  Purchase #4 $84.61   10.420%   $93.4264   $93.43   $93.45   $93.40  
  Purchase #5 $239.71   10.713%   $265.3901   $265.39   $265.40   $265.40  
  Purchase #6 $22.36   11.185%   $24.861   $24.86   $24.85   $24.90  
  Purchase #7 $147.64   4.857%   $154.8109   $154.81   $154.80   $154.80  
  7 purchase totals = $1,046.72       $1,119.2808   $1,119.28   $1,119.25   $1,119.30