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 $54.82   13.790%   $62.3797   $62.38   $62.40   $62.40  
  Purchase #2 $208.61   11.354%   $232.2956   $232.30   $232.30   $232.30  
  Purchase #3 $43.57   12.678%   $49.0938   $49.09   $49.10   $49.10  
  Purchase #4 $248.96   10.856%   $275.9871   $275.99   $276.00   $276.00  
  Purchase #5 $192.33   6.175%   $204.2064   $204.21   $204.20   $204.20  
  Purchase #6 $49.80   3.540%   $51.5629   $51.56   $51.55   $51.60  
  Purchase #7 $224.40   9.577%   $245.8908   $245.89   $245.90   $245.90  
  7 purchase totals = $1,022.49       $1,121.4163   $1,121.42   $1,121.45   $1,121.50